Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.c
4 : * buffer manager interface routines
5 : *
6 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/storage/buffer/bufmgr.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : /*
16 : * Principal entry points:
17 : *
18 : * ReadBuffer() -- find or create a buffer holding the requested page,
19 : * and pin it so that no one can destroy it while this process
20 : * is using it.
21 : *
22 : * StartReadBuffer() -- as above, with separate wait step
23 : * StartReadBuffers() -- multiple block version
24 : * WaitReadBuffers() -- second step of above
25 : *
26 : * ReleaseBuffer() -- unpin a buffer
27 : *
28 : * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
29 : * The disk write is delayed until buffer replacement or checkpoint.
30 : *
31 : * See also these files:
32 : * freelist.c -- chooses victim for buffer replacement
33 : * buf_table.c -- manages the buffer lookup table
34 : */
35 : #include "postgres.h"
36 :
37 : #include <sys/file.h>
38 : #include <unistd.h>
39 :
40 : #include "access/tableam.h"
41 : #include "access/xloginsert.h"
42 : #include "access/xlogutils.h"
43 : #ifdef USE_ASSERT_CHECKING
44 : #include "catalog/pg_tablespace_d.h"
45 : #endif
46 : #include "catalog/storage.h"
47 : #include "catalog/storage_xlog.h"
48 : #include "executor/instrument.h"
49 : #include "lib/binaryheap.h"
50 : #include "miscadmin.h"
51 : #include "pg_trace.h"
52 : #include "pgstat.h"
53 : #include "postmaster/bgwriter.h"
54 : #include "storage/aio.h"
55 : #include "storage/buf_internals.h"
56 : #include "storage/bufmgr.h"
57 : #include "storage/fd.h"
58 : #include "storage/ipc.h"
59 : #include "storage/lmgr.h"
60 : #include "storage/proc.h"
61 : #include "storage/read_stream.h"
62 : #include "storage/smgr.h"
63 : #include "storage/standby.h"
64 : #include "utils/memdebug.h"
65 : #include "utils/ps_status.h"
66 : #include "utils/rel.h"
67 : #include "utils/resowner.h"
68 : #include "utils/timestamp.h"
69 :
70 :
71 : /* Note: these two macros only work on shared buffers, not local ones! */
72 : #define BufHdrGetBlock(bufHdr) ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
73 : #define BufferGetLSN(bufHdr) (PageGetLSN(BufHdrGetBlock(bufHdr)))
74 :
75 : /* Note: this macro only works on local buffers, not shared ones! */
76 : #define LocalBufHdrGetBlock(bufHdr) \
77 : LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
78 :
79 : /* Bits in SyncOneBuffer's return value */
80 : #define BUF_WRITTEN 0x01
81 : #define BUF_REUSABLE 0x02
82 :
83 : #define RELS_BSEARCH_THRESHOLD 20
84 :
85 : /*
86 : * This is the size (in the number of blocks) above which we scan the
87 : * entire buffer pool to remove the buffers for all the pages of relation
88 : * being dropped. For the relations with size below this threshold, we find
89 : * the buffers by doing lookups in BufMapping table.
90 : */
91 : #define BUF_DROP_FULL_SCAN_THRESHOLD (uint64) (NBuffers / 32)
92 :
93 : typedef struct PrivateRefCountEntry
94 : {
95 : Buffer buffer;
96 : int32 refcount;
97 : } PrivateRefCountEntry;
98 :
99 : /* 64 bytes, about the size of a cache line on common systems */
100 : #define REFCOUNT_ARRAY_ENTRIES 8
101 :
102 : /*
103 : * Status of buffers to checkpoint for a particular tablespace, used
104 : * internally in BufferSync.
105 : */
106 : typedef struct CkptTsStatus
107 : {
108 : /* oid of the tablespace */
109 : Oid tsId;
110 :
111 : /*
112 : * Checkpoint progress for this tablespace. To make progress comparable
113 : * between tablespaces the progress is, for each tablespace, measured as a
114 : * number between 0 and the total number of to-be-checkpointed pages. Each
115 : * page checkpointed in this tablespace increments this space's progress
116 : * by progress_slice.
117 : */
118 : float8 progress;
119 : float8 progress_slice;
120 :
121 : /* number of to-be checkpointed pages in this tablespace */
122 : int num_to_scan;
123 : /* already processed pages in this tablespace */
124 : int num_scanned;
125 :
126 : /* current offset in CkptBufferIds for this tablespace */
127 : int index;
128 : } CkptTsStatus;
129 :
130 : /*
131 : * Type for array used to sort SMgrRelations
132 : *
133 : * FlushRelationsAllBuffers shares the same comparator function with
134 : * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
135 : * compatible.
136 : */
137 : typedef struct SMgrSortArray
138 : {
139 : RelFileLocator rlocator; /* This must be the first member */
140 : SMgrRelation srel;
141 : } SMgrSortArray;
142 :
143 : /* GUC variables */
144 : bool zero_damaged_pages = false;
145 : int bgwriter_lru_maxpages = 100;
146 : double bgwriter_lru_multiplier = 2.0;
147 : bool track_io_timing = false;
148 :
149 : /*
150 : * How many buffers PrefetchBuffer callers should try to stay ahead of their
151 : * ReadBuffer calls by. Zero means "never prefetch". This value is only used
152 : * for buffers not belonging to tablespaces that have their
153 : * effective_io_concurrency parameter set.
154 : */
155 : int effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
156 :
157 : /*
158 : * Like effective_io_concurrency, but used by maintenance code paths that might
159 : * benefit from a higher setting because they work on behalf of many sessions.
160 : * Overridden by the tablespace setting of the same name.
161 : */
162 : int maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
163 :
164 : /*
165 : * Limit on how many blocks should be handled in single I/O operations.
166 : * StartReadBuffers() callers should respect it, as should other operations
167 : * that call smgr APIs directly. It is computed as the minimum of underlying
168 : * GUCs io_combine_limit_guc and io_max_combine_limit.
169 : */
170 : int io_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
171 : int io_combine_limit_guc = DEFAULT_IO_COMBINE_LIMIT;
172 : int io_max_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
173 :
174 : /*
175 : * GUC variables about triggering kernel writeback for buffers written; OS
176 : * dependent defaults are set via the GUC mechanism.
177 : */
178 : int checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
179 : int bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
180 : int backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
181 :
182 : /* local state for LockBufferForCleanup */
183 : static BufferDesc *PinCountWaitBuf = NULL;
184 :
185 : /*
186 : * Backend-Private refcount management:
187 : *
188 : * Each buffer also has a private refcount that keeps track of the number of
189 : * times the buffer is pinned in the current process. This is so that the
190 : * shared refcount needs to be modified only once if a buffer is pinned more
191 : * than once by an individual backend. It's also used to check that no buffers
192 : * are still pinned at the end of transactions and when exiting.
193 : *
194 : *
195 : * To avoid - as we used to - requiring an array with NBuffers entries to keep
196 : * track of local buffers, we use a small sequentially searched array
197 : * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
198 : * keep track of backend local pins.
199 : *
200 : * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
201 : * refcounts are kept track of in the array; after that, new array entries
202 : * displace old ones into the hash table. That way a frequently used entry
203 : * can't get "stuck" in the hashtable while infrequent ones clog the array.
204 : *
205 : * Note that in most scenarios the number of pinned buffers will not exceed
206 : * REFCOUNT_ARRAY_ENTRIES.
207 : *
208 : *
209 : * To enter a buffer into the refcount tracking mechanism first reserve a free
210 : * entry using ReservePrivateRefCountEntry() and then later, if necessary,
211 : * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
212 : * memory allocations in NewPrivateRefCountEntry() which can be important
213 : * because in some scenarios it's called with a spinlock held...
214 : */
215 : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
216 : static HTAB *PrivateRefCountHash = NULL;
217 : static int32 PrivateRefCountOverflowed = 0;
218 : static uint32 PrivateRefCountClock = 0;
219 : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
220 :
221 : static uint32 MaxProportionalPins;
222 :
223 : static void ReservePrivateRefCountEntry(void);
224 : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
225 : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
226 : static inline int32 GetPrivateRefCount(Buffer buffer);
227 : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
228 :
229 : /* ResourceOwner callbacks to hold in-progress I/Os and buffer pins */
230 : static void ResOwnerReleaseBufferIO(Datum res);
231 : static char *ResOwnerPrintBufferIO(Datum res);
232 : static void ResOwnerReleaseBufferPin(Datum res);
233 : static char *ResOwnerPrintBufferPin(Datum res);
234 :
235 : const ResourceOwnerDesc buffer_io_resowner_desc =
236 : {
237 : .name = "buffer io",
238 : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
239 : .release_priority = RELEASE_PRIO_BUFFER_IOS,
240 : .ReleaseResource = ResOwnerReleaseBufferIO,
241 : .DebugPrint = ResOwnerPrintBufferIO
242 : };
243 :
244 : const ResourceOwnerDesc buffer_pin_resowner_desc =
245 : {
246 : .name = "buffer pin",
247 : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
248 : .release_priority = RELEASE_PRIO_BUFFER_PINS,
249 : .ReleaseResource = ResOwnerReleaseBufferPin,
250 : .DebugPrint = ResOwnerPrintBufferPin
251 : };
252 :
253 : /*
254 : * Ensure that the PrivateRefCountArray has sufficient space to store one more
255 : * entry. This has to be called before using NewPrivateRefCountEntry() to fill
256 : * a new entry - but it's perfectly fine to not use a reserved entry.
257 : */
258 : static void
259 127937338 : ReservePrivateRefCountEntry(void)
260 : {
261 : /* Already reserved (or freed), nothing to do */
262 127937338 : if (ReservedRefCountEntry != NULL)
263 119763650 : return;
264 :
265 : /*
266 : * First search for a free entry the array, that'll be sufficient in the
267 : * majority of cases.
268 : */
269 : {
270 : int i;
271 :
272 20751920 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
273 : {
274 : PrivateRefCountEntry *res;
275 :
276 20417410 : res = &PrivateRefCountArray[i];
277 :
278 20417410 : if (res->buffer == InvalidBuffer)
279 : {
280 7839178 : ReservedRefCountEntry = res;
281 7839178 : return;
282 : }
283 : }
284 : }
285 :
286 : /*
287 : * No luck. All array entries are full. Move one array entry into the hash
288 : * table.
289 : */
290 : {
291 : /*
292 : * Move entry from the current clock position in the array into the
293 : * hashtable. Use that slot.
294 : */
295 : PrivateRefCountEntry *hashent;
296 : bool found;
297 :
298 : /* select victim slot */
299 334510 : ReservedRefCountEntry =
300 334510 : &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
301 :
302 : /* Better be used, otherwise we shouldn't get here. */
303 : Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
304 :
305 : /* enter victim array entry into hashtable */
306 334510 : hashent = hash_search(PrivateRefCountHash,
307 334510 : &(ReservedRefCountEntry->buffer),
308 : HASH_ENTER,
309 : &found);
310 : Assert(!found);
311 334510 : hashent->refcount = ReservedRefCountEntry->refcount;
312 :
313 : /* clear the now free array slot */
314 334510 : ReservedRefCountEntry->buffer = InvalidBuffer;
315 334510 : ReservedRefCountEntry->refcount = 0;
316 :
317 334510 : PrivateRefCountOverflowed++;
318 : }
319 : }
320 :
321 : /*
322 : * Fill a previously reserved refcount entry.
323 : */
324 : static PrivateRefCountEntry *
325 116467828 : NewPrivateRefCountEntry(Buffer buffer)
326 : {
327 : PrivateRefCountEntry *res;
328 :
329 : /* only allowed to be called when a reservation has been made */
330 : Assert(ReservedRefCountEntry != NULL);
331 :
332 : /* use up the reserved entry */
333 116467828 : res = ReservedRefCountEntry;
334 116467828 : ReservedRefCountEntry = NULL;
335 :
336 : /* and fill it */
337 116467828 : res->buffer = buffer;
338 116467828 : res->refcount = 0;
339 :
340 116467828 : return res;
341 : }
342 :
343 : /*
344 : * Return the PrivateRefCount entry for the passed buffer.
345 : *
346 : * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
347 : * do_move is true, and the entry resides in the hashtable the entry is
348 : * optimized for frequent access by moving it to the array.
349 : */
350 : static PrivateRefCountEntry *
351 287446980 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
352 : {
353 : PrivateRefCountEntry *res;
354 : int i;
355 :
356 : Assert(BufferIsValid(buffer));
357 : Assert(!BufferIsLocal(buffer));
358 :
359 : /*
360 : * First search for references in the array, that'll be sufficient in the
361 : * majority of cases.
362 : */
363 1353647906 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
364 : {
365 1241201570 : res = &PrivateRefCountArray[i];
366 :
367 1241201570 : if (res->buffer == buffer)
368 175000644 : return res;
369 : }
370 :
371 : /*
372 : * By here we know that the buffer, if already pinned, isn't residing in
373 : * the array.
374 : *
375 : * Only look up the buffer in the hashtable if we've previously overflowed
376 : * into it.
377 : */
378 112446336 : if (PrivateRefCountOverflowed == 0)
379 111631422 : return NULL;
380 :
381 814914 : res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
382 :
383 814914 : if (res == NULL)
384 476334 : return NULL;
385 338580 : else if (!do_move)
386 : {
387 : /* caller doesn't want us to move the hash entry into the array */
388 298488 : return res;
389 : }
390 : else
391 : {
392 : /* move buffer from hashtable into the free array slot */
393 : bool found;
394 : PrivateRefCountEntry *free;
395 :
396 : /* Ensure there's a free array slot */
397 40092 : ReservePrivateRefCountEntry();
398 :
399 : /* Use up the reserved slot */
400 : Assert(ReservedRefCountEntry != NULL);
401 40092 : free = ReservedRefCountEntry;
402 40092 : ReservedRefCountEntry = NULL;
403 : Assert(free->buffer == InvalidBuffer);
404 :
405 : /* and fill it */
406 40092 : free->buffer = buffer;
407 40092 : free->refcount = res->refcount;
408 :
409 : /* delete from hashtable */
410 40092 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
411 : Assert(found);
412 : Assert(PrivateRefCountOverflowed > 0);
413 40092 : PrivateRefCountOverflowed--;
414 :
415 40092 : return free;
416 : }
417 : }
418 :
419 : /*
420 : * Returns how many times the passed buffer is pinned by this backend.
421 : *
422 : * Only works for shared memory buffers!
423 : */
424 : static inline int32
425 6052268 : GetPrivateRefCount(Buffer buffer)
426 : {
427 : PrivateRefCountEntry *ref;
428 :
429 : Assert(BufferIsValid(buffer));
430 : Assert(!BufferIsLocal(buffer));
431 :
432 : /*
433 : * Not moving the entry - that's ok for the current users, but we might
434 : * want to change this one day.
435 : */
436 6052268 : ref = GetPrivateRefCountEntry(buffer, false);
437 :
438 6052268 : if (ref == NULL)
439 8940 : return 0;
440 6043328 : return ref->refcount;
441 : }
442 :
443 : /*
444 : * Release resources used to track the reference count of a buffer which we no
445 : * longer have pinned and don't want to pin again immediately.
446 : */
447 : static void
448 116467828 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
449 : {
450 : Assert(ref->refcount == 0);
451 :
452 116467828 : if (ref >= &PrivateRefCountArray[0] &&
453 : ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
454 : {
455 116173410 : ref->buffer = InvalidBuffer;
456 :
457 : /*
458 : * Mark the just used entry as reserved - in many scenarios that
459 : * allows us to avoid ever having to search the array/hash for free
460 : * entries.
461 : */
462 116173410 : ReservedRefCountEntry = ref;
463 : }
464 : else
465 : {
466 : bool found;
467 294418 : Buffer buffer = ref->buffer;
468 :
469 294418 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
470 : Assert(found);
471 : Assert(PrivateRefCountOverflowed > 0);
472 294418 : PrivateRefCountOverflowed--;
473 : }
474 116467828 : }
475 :
476 : /*
477 : * BufferIsPinned
478 : * True iff the buffer is pinned (also checks for valid buffer number).
479 : *
480 : * NOTE: what we check here is that *this* backend holds a pin on
481 : * the buffer. We do not care whether some other backend does.
482 : */
483 : #define BufferIsPinned(bufnum) \
484 : ( \
485 : !BufferIsValid(bufnum) ? \
486 : false \
487 : : \
488 : BufferIsLocal(bufnum) ? \
489 : (LocalRefCount[-(bufnum) - 1] > 0) \
490 : : \
491 : (GetPrivateRefCount(bufnum) > 0) \
492 : )
493 :
494 :
495 : static Buffer ReadBuffer_common(Relation rel,
496 : SMgrRelation smgr, char smgr_persistence,
497 : ForkNumber forkNum, BlockNumber blockNum,
498 : ReadBufferMode mode, BufferAccessStrategy strategy);
499 : static BlockNumber ExtendBufferedRelCommon(BufferManagerRelation bmr,
500 : ForkNumber fork,
501 : BufferAccessStrategy strategy,
502 : uint32 flags,
503 : uint32 extend_by,
504 : BlockNumber extend_upto,
505 : Buffer *buffers,
506 : uint32 *extended_by);
507 : static BlockNumber ExtendBufferedRelShared(BufferManagerRelation bmr,
508 : ForkNumber fork,
509 : BufferAccessStrategy strategy,
510 : uint32 flags,
511 : uint32 extend_by,
512 : BlockNumber extend_upto,
513 : Buffer *buffers,
514 : uint32 *extended_by);
515 : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
516 : static void PinBuffer_Locked(BufferDesc *buf);
517 : static void UnpinBuffer(BufferDesc *buf);
518 : static void UnpinBufferNoOwner(BufferDesc *buf);
519 : static void BufferSync(int flags);
520 : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
521 : static int SyncOneBuffer(int buf_id, bool skip_recently_used,
522 : WritebackContext *wb_context);
523 : static void WaitIO(BufferDesc *buf);
524 : static void AbortBufferIO(Buffer buffer);
525 : static void shared_buffer_write_error_callback(void *arg);
526 : static void local_buffer_write_error_callback(void *arg);
527 : static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
528 : char relpersistence,
529 : ForkNumber forkNum,
530 : BlockNumber blockNum,
531 : BufferAccessStrategy strategy,
532 : bool *foundPtr, IOContext io_context);
533 : static bool AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress);
534 : static void CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete);
535 : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
536 : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
537 : IOObject io_object, IOContext io_context);
538 : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
539 : ForkNumber forkNum,
540 : BlockNumber nForkBlock,
541 : BlockNumber firstDelBlock);
542 : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
543 : RelFileLocator dstlocator,
544 : ForkNumber forkNum, bool permanent);
545 : static void AtProcExit_Buffers(int code, Datum arg);
546 : static void CheckForBufferLeaks(void);
547 : #ifdef USE_ASSERT_CHECKING
548 : static void AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
549 : void *unused_context);
550 : #endif
551 : static int rlocator_comparator(const void *p1, const void *p2);
552 : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
553 : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
554 : static int ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
555 :
556 :
557 : /*
558 : * Implementation of PrefetchBuffer() for shared buffers.
559 : */
560 : PrefetchBufferResult
561 60906 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
562 : ForkNumber forkNum,
563 : BlockNumber blockNum)
564 : {
565 60906 : PrefetchBufferResult result = {InvalidBuffer, false};
566 : BufferTag newTag; /* identity of requested block */
567 : uint32 newHash; /* hash value for newTag */
568 : LWLock *newPartitionLock; /* buffer partition lock for it */
569 : int buf_id;
570 :
571 : Assert(BlockNumberIsValid(blockNum));
572 :
573 : /* create a tag so we can lookup the buffer */
574 60906 : InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
575 : forkNum, blockNum);
576 :
577 : /* determine its hash code and partition lock ID */
578 60906 : newHash = BufTableHashCode(&newTag);
579 60906 : newPartitionLock = BufMappingPartitionLock(newHash);
580 :
581 : /* see if the block is in the buffer pool already */
582 60906 : LWLockAcquire(newPartitionLock, LW_SHARED);
583 60906 : buf_id = BufTableLookup(&newTag, newHash);
584 60906 : LWLockRelease(newPartitionLock);
585 :
586 : /* If not in buffers, initiate prefetch */
587 60906 : if (buf_id < 0)
588 : {
589 : #ifdef USE_PREFETCH
590 : /*
591 : * Try to initiate an asynchronous read. This returns false in
592 : * recovery if the relation file doesn't exist.
593 : */
594 34414 : if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
595 16982 : smgrprefetch(smgr_reln, forkNum, blockNum, 1))
596 : {
597 16982 : result.initiated_io = true;
598 : }
599 : #endif /* USE_PREFETCH */
600 : }
601 : else
602 : {
603 : /*
604 : * Report the buffer it was in at that time. The caller may be able
605 : * to avoid a buffer table lookup, but it's not pinned and it must be
606 : * rechecked!
607 : */
608 43474 : result.recent_buffer = buf_id + 1;
609 : }
610 :
611 : /*
612 : * If the block *is* in buffers, we do nothing. This is not really ideal:
613 : * the block might be just about to be evicted, which would be stupid
614 : * since we know we are going to need it soon. But the only easy answer
615 : * is to bump the usage_count, which does not seem like a great solution:
616 : * when the caller does ultimately touch the block, usage_count would get
617 : * bumped again, resulting in too much favoritism for blocks that are
618 : * involved in a prefetch sequence. A real fix would involve some
619 : * additional per-buffer state, and it's not clear that there's enough of
620 : * a problem to justify that.
621 : */
622 :
623 60906 : return result;
624 : }
625 :
626 : /*
627 : * PrefetchBuffer -- initiate asynchronous read of a block of a relation
628 : *
629 : * This is named by analogy to ReadBuffer but doesn't actually allocate a
630 : * buffer. Instead it tries to ensure that a future ReadBuffer for the given
631 : * block will not be delayed by the I/O. Prefetching is optional.
632 : *
633 : * There are three possible outcomes:
634 : *
635 : * 1. If the block is already cached, the result includes a valid buffer that
636 : * could be used by the caller to avoid the need for a later buffer lookup, but
637 : * it's not pinned, so the caller must recheck it.
638 : *
639 : * 2. If the kernel has been asked to initiate I/O, the initiated_io member is
640 : * true. Currently there is no way to know if the data was already cached by
641 : * the kernel and therefore didn't really initiate I/O, and no way to know when
642 : * the I/O completes other than using synchronous ReadBuffer().
643 : *
644 : * 3. Otherwise, the buffer wasn't already cached by PostgreSQL, and
645 : * USE_PREFETCH is not defined (this build doesn't support prefetching due to
646 : * lack of a kernel facility), direct I/O is enabled, or the underlying
647 : * relation file wasn't found and we are in recovery. (If the relation file
648 : * wasn't found and we are not in recovery, an error is raised).
649 : */
650 : PrefetchBufferResult
651 39890 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
652 : {
653 : Assert(RelationIsValid(reln));
654 : Assert(BlockNumberIsValid(blockNum));
655 :
656 39890 : if (RelationUsesLocalBuffers(reln))
657 : {
658 : /* see comments in ReadBufferExtended */
659 1566 : if (RELATION_IS_OTHER_TEMP(reln))
660 0 : ereport(ERROR,
661 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
662 : errmsg("cannot access temporary tables of other sessions")));
663 :
664 : /* pass it off to localbuf.c */
665 1566 : return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
666 : }
667 : else
668 : {
669 : /* pass it to the shared buffer version */
670 38324 : return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
671 : }
672 : }
673 :
674 : /*
675 : * ReadRecentBuffer -- try to pin a block in a recently observed buffer
676 : *
677 : * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
678 : * successful. Return true if the buffer is valid and still has the expected
679 : * tag. In that case, the buffer is pinned and the usage count is bumped.
680 : */
681 : bool
682 8944 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
683 : Buffer recent_buffer)
684 : {
685 : BufferDesc *bufHdr;
686 : BufferTag tag;
687 : uint32 buf_state;
688 : bool have_private_ref;
689 :
690 : Assert(BufferIsValid(recent_buffer));
691 :
692 8944 : ResourceOwnerEnlarge(CurrentResourceOwner);
693 8944 : ReservePrivateRefCountEntry();
694 8944 : InitBufferTag(&tag, &rlocator, forkNum, blockNum);
695 :
696 8944 : if (BufferIsLocal(recent_buffer))
697 : {
698 64 : int b = -recent_buffer - 1;
699 :
700 64 : bufHdr = GetLocalBufferDescriptor(b);
701 64 : buf_state = pg_atomic_read_u32(&bufHdr->state);
702 :
703 : /* Is it still valid and holding the right tag? */
704 64 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
705 : {
706 64 : PinLocalBuffer(bufHdr, true);
707 :
708 64 : pgBufferUsage.local_blks_hit++;
709 :
710 64 : return true;
711 : }
712 : }
713 : else
714 : {
715 8880 : bufHdr = GetBufferDescriptor(recent_buffer - 1);
716 8880 : have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
717 :
718 : /*
719 : * Do we already have this buffer pinned with a private reference? If
720 : * so, it must be valid and it is safe to check the tag without
721 : * locking. If not, we have to lock the header first and then check.
722 : */
723 8880 : if (have_private_ref)
724 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
725 : else
726 8880 : buf_state = LockBufHdr(bufHdr);
727 :
728 8880 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
729 : {
730 : /*
731 : * It's now safe to pin the buffer. We can't pin first and ask
732 : * questions later, because it might confuse code paths like
733 : * InvalidateBuffer() if we pinned a random non-matching buffer.
734 : */
735 8760 : if (have_private_ref)
736 0 : PinBuffer(bufHdr, NULL); /* bump pin count */
737 : else
738 8760 : PinBuffer_Locked(bufHdr); /* pin for first time */
739 :
740 8760 : pgBufferUsage.shared_blks_hit++;
741 :
742 8760 : return true;
743 : }
744 :
745 : /* If we locked the header above, now unlock. */
746 120 : if (!have_private_ref)
747 120 : UnlockBufHdr(bufHdr, buf_state);
748 : }
749 :
750 120 : return false;
751 : }
752 :
753 : /*
754 : * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
755 : * fork with RBM_NORMAL mode and default strategy.
756 : */
757 : Buffer
758 85100628 : ReadBuffer(Relation reln, BlockNumber blockNum)
759 : {
760 85100628 : return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
761 : }
762 :
763 : /*
764 : * ReadBufferExtended -- returns a buffer containing the requested
765 : * block of the requested relation. If the blknum
766 : * requested is P_NEW, extend the relation file and
767 : * allocate a new block. (Caller is responsible for
768 : * ensuring that only one backend tries to extend a
769 : * relation at the same time!)
770 : *
771 : * Returns: the buffer number for the buffer containing
772 : * the block read. The returned buffer has been pinned.
773 : * Does not return on error --- elog's instead.
774 : *
775 : * Assume when this function is called, that reln has been opened already.
776 : *
777 : * In RBM_NORMAL mode, the page is read from disk, and the page header is
778 : * validated. An error is thrown if the page header is not valid. (But
779 : * note that an all-zero page is considered "valid"; see
780 : * PageIsVerified().)
781 : *
782 : * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
783 : * valid, the page is zeroed instead of throwing an error. This is intended
784 : * for non-critical data, where the caller is prepared to repair errors.
785 : *
786 : * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
787 : * filled with zeros instead of reading it from disk. Useful when the caller
788 : * is going to fill the page from scratch, since this saves I/O and avoids
789 : * unnecessary failure if the page-on-disk has corrupt page headers.
790 : * The page is returned locked to ensure that the caller has a chance to
791 : * initialize the page before it's made visible to others.
792 : * Caution: do not use this mode to read a page that is beyond the relation's
793 : * current physical EOF; that is likely to cause problems in md.c when
794 : * the page is modified and written out. P_NEW is OK, though.
795 : *
796 : * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
797 : * a cleanup-strength lock on the page.
798 : *
799 : * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
800 : *
801 : * If strategy is not NULL, a nondefault buffer access strategy is used.
802 : * See buffer/README for details.
803 : */
804 : inline Buffer
805 102833106 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
806 : ReadBufferMode mode, BufferAccessStrategy strategy)
807 : {
808 : Buffer buf;
809 :
810 : /*
811 : * Reject attempts to read non-local temporary relations; we would be
812 : * likely to get wrong data since we have no visibility into the owning
813 : * session's local buffers.
814 : */
815 102833106 : if (RELATION_IS_OTHER_TEMP(reln))
816 0 : ereport(ERROR,
817 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
818 : errmsg("cannot access temporary tables of other sessions")));
819 :
820 : /*
821 : * Read the buffer, and update pgstat counters to reflect a cache hit or
822 : * miss.
823 : */
824 102833106 : buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
825 : forkNum, blockNum, mode, strategy);
826 :
827 102833060 : return buf;
828 : }
829 :
830 :
831 : /*
832 : * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
833 : * a relcache entry for the relation.
834 : *
835 : * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
836 : * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
837 : * cannot be used for temporary relations (and making that work might be
838 : * difficult, unless we only want to read temporary relations for our own
839 : * ProcNumber).
840 : */
841 : Buffer
842 11335706 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
843 : BlockNumber blockNum, ReadBufferMode mode,
844 : BufferAccessStrategy strategy, bool permanent)
845 : {
846 11335706 : SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
847 :
848 11335706 : return ReadBuffer_common(NULL, smgr,
849 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
850 : forkNum, blockNum,
851 : mode, strategy);
852 : }
853 :
854 : /*
855 : * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
856 : */
857 : Buffer
858 90428 : ExtendBufferedRel(BufferManagerRelation bmr,
859 : ForkNumber forkNum,
860 : BufferAccessStrategy strategy,
861 : uint32 flags)
862 : {
863 : Buffer buf;
864 90428 : uint32 extend_by = 1;
865 :
866 90428 : ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
867 : &buf, &extend_by);
868 :
869 90428 : return buf;
870 : }
871 :
872 : /*
873 : * Extend relation by multiple blocks.
874 : *
875 : * Tries to extend the relation by extend_by blocks. Depending on the
876 : * availability of resources the relation may end up being extended by a
877 : * smaller number of pages (unless an error is thrown, always by at least one
878 : * page). *extended_by is updated to the number of pages the relation has been
879 : * extended to.
880 : *
881 : * buffers needs to be an array that is at least extend_by long. Upon
882 : * completion, the first extend_by array elements will point to a pinned
883 : * buffer.
884 : *
885 : * If EB_LOCK_FIRST is part of flags, the first returned buffer is
886 : * locked. This is useful for callers that want a buffer that is guaranteed to
887 : * be empty.
888 : */
889 : BlockNumber
890 317460 : ExtendBufferedRelBy(BufferManagerRelation bmr,
891 : ForkNumber fork,
892 : BufferAccessStrategy strategy,
893 : uint32 flags,
894 : uint32 extend_by,
895 : Buffer *buffers,
896 : uint32 *extended_by)
897 : {
898 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
899 : Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
900 : Assert(extend_by > 0);
901 :
902 317460 : if (bmr.smgr == NULL)
903 : {
904 317460 : bmr.smgr = RelationGetSmgr(bmr.rel);
905 317460 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
906 : }
907 :
908 317460 : return ExtendBufferedRelCommon(bmr, fork, strategy, flags,
909 : extend_by, InvalidBlockNumber,
910 : buffers, extended_by);
911 : }
912 :
913 : /*
914 : * Extend the relation so it is at least extend_to blocks large, return buffer
915 : * (extend_to - 1).
916 : *
917 : * This is useful for callers that want to write a specific page, regardless
918 : * of the current size of the relation (e.g. useful for visibilitymap and for
919 : * crash recovery).
920 : */
921 : Buffer
922 102580 : ExtendBufferedRelTo(BufferManagerRelation bmr,
923 : ForkNumber fork,
924 : BufferAccessStrategy strategy,
925 : uint32 flags,
926 : BlockNumber extend_to,
927 : ReadBufferMode mode)
928 : {
929 : BlockNumber current_size;
930 102580 : uint32 extended_by = 0;
931 102580 : Buffer buffer = InvalidBuffer;
932 : Buffer buffers[64];
933 :
934 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
935 : Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
936 : Assert(extend_to != InvalidBlockNumber && extend_to > 0);
937 :
938 102580 : if (bmr.smgr == NULL)
939 : {
940 13976 : bmr.smgr = RelationGetSmgr(bmr.rel);
941 13976 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
942 : }
943 :
944 : /*
945 : * If desired, create the file if it doesn't exist. If
946 : * smgr_cached_nblocks[fork] is positive then it must exist, no need for
947 : * an smgrexists call.
948 : */
949 102580 : if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
950 13976 : (bmr.smgr->smgr_cached_nblocks[fork] == 0 ||
951 34 : bmr.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
952 13942 : !smgrexists(bmr.smgr, fork))
953 : {
954 13922 : LockRelationForExtension(bmr.rel, ExclusiveLock);
955 :
956 : /* recheck, fork might have been created concurrently */
957 13922 : if (!smgrexists(bmr.smgr, fork))
958 13920 : smgrcreate(bmr.smgr, fork, flags & EB_PERFORMING_RECOVERY);
959 :
960 13922 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
961 : }
962 :
963 : /*
964 : * If requested, invalidate size cache, so that smgrnblocks asks the
965 : * kernel.
966 : */
967 102580 : if (flags & EB_CLEAR_SIZE_CACHE)
968 13976 : bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
969 :
970 : /*
971 : * Estimate how many pages we'll need to extend by. This avoids acquiring
972 : * unnecessarily many victim buffers.
973 : */
974 102580 : current_size = smgrnblocks(bmr.smgr, fork);
975 :
976 : /*
977 : * Since no-one else can be looking at the page contents yet, there is no
978 : * difference between an exclusive lock and a cleanup-strength lock. Note
979 : * that we pass the original mode to ReadBuffer_common() below, when
980 : * falling back to reading the buffer to a concurrent relation extension.
981 : */
982 102580 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
983 87882 : flags |= EB_LOCK_TARGET;
984 :
985 209356 : while (current_size < extend_to)
986 : {
987 106776 : uint32 num_pages = lengthof(buffers);
988 : BlockNumber first_block;
989 :
990 106776 : if ((uint64) current_size + num_pages > extend_to)
991 106644 : num_pages = extend_to - current_size;
992 :
993 106776 : first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
994 : num_pages, extend_to,
995 : buffers, &extended_by);
996 :
997 106776 : current_size = first_block + extended_by;
998 : Assert(num_pages != 0 || current_size >= extend_to);
999 :
1000 227844 : for (uint32 i = 0; i < extended_by; i++)
1001 : {
1002 121068 : if (first_block + i != extend_to - 1)
1003 18494 : ReleaseBuffer(buffers[i]);
1004 : else
1005 102574 : buffer = buffers[i];
1006 : }
1007 : }
1008 :
1009 : /*
1010 : * It's possible that another backend concurrently extended the relation.
1011 : * In that case read the buffer.
1012 : *
1013 : * XXX: Should we control this via a flag?
1014 : */
1015 102580 : if (buffer == InvalidBuffer)
1016 : {
1017 : Assert(extended_by == 0);
1018 6 : buffer = ReadBuffer_common(bmr.rel, bmr.smgr, bmr.relpersistence,
1019 : fork, extend_to - 1, mode, strategy);
1020 : }
1021 :
1022 102580 : return buffer;
1023 : }
1024 :
1025 : /*
1026 : * Lock and optionally zero a buffer, as part of the implementation of
1027 : * RBM_ZERO_AND_LOCK or RBM_ZERO_AND_CLEANUP_LOCK. The buffer must be already
1028 : * pinned. If the buffer is not already valid, it is zeroed and made valid.
1029 : */
1030 : static void
1031 622878 : ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
1032 : {
1033 : BufferDesc *bufHdr;
1034 : bool need_to_zero;
1035 622878 : bool isLocalBuf = BufferIsLocal(buffer);
1036 :
1037 : Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
1038 :
1039 622878 : if (already_valid)
1040 : {
1041 : /*
1042 : * If the caller already knew the buffer was valid, we can skip some
1043 : * header interaction. The caller just wants to lock the buffer.
1044 : */
1045 73644 : need_to_zero = false;
1046 : }
1047 549234 : else if (isLocalBuf)
1048 : {
1049 : /* Simple case for non-shared buffers. */
1050 48 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
1051 48 : need_to_zero = StartLocalBufferIO(bufHdr, true, false);
1052 : }
1053 : else
1054 : {
1055 : /*
1056 : * Take BM_IO_IN_PROGRESS, or discover that BM_VALID has been set
1057 : * concurrently. Even though we aren't doing I/O, that ensures that
1058 : * we don't zero a page that someone else has pinned. An exclusive
1059 : * content lock wouldn't be enough, because readers are allowed to
1060 : * drop the content lock after determining that a tuple is visible
1061 : * (see buffer access rules in README).
1062 : */
1063 549186 : bufHdr = GetBufferDescriptor(buffer - 1);
1064 549186 : need_to_zero = StartBufferIO(bufHdr, true, false);
1065 : }
1066 :
1067 622878 : if (need_to_zero)
1068 : {
1069 549234 : memset(BufferGetPage(buffer), 0, BLCKSZ);
1070 :
1071 : /*
1072 : * Grab the buffer content lock before marking the page as valid, to
1073 : * make sure that no other backend sees the zeroed page before the
1074 : * caller has had a chance to initialize it.
1075 : *
1076 : * Since no-one else can be looking at the page contents yet, there is
1077 : * no difference between an exclusive lock and a cleanup-strength
1078 : * lock. (Note that we cannot use LockBuffer() or
1079 : * LockBufferForCleanup() here, because they assert that the buffer is
1080 : * already valid.)
1081 : */
1082 549234 : if (!isLocalBuf)
1083 549186 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
1084 :
1085 : /* Set BM_VALID, terminate IO, and wake up any waiters */
1086 549234 : if (isLocalBuf)
1087 48 : TerminateLocalBufferIO(bufHdr, false, BM_VALID, false);
1088 : else
1089 549186 : TerminateBufferIO(bufHdr, false, BM_VALID, true, false);
1090 : }
1091 73644 : else if (!isLocalBuf)
1092 : {
1093 : /*
1094 : * The buffer is valid, so we can't zero it. The caller still expects
1095 : * the page to be locked on return.
1096 : */
1097 73604 : if (mode == RBM_ZERO_AND_LOCK)
1098 73514 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
1099 : else
1100 90 : LockBufferForCleanup(buffer);
1101 : }
1102 622878 : }
1103 :
1104 : /*
1105 : * Pin a buffer for a given block. *foundPtr is set to true if the block was
1106 : * already present, or false if more work is required to either read it in or
1107 : * zero it.
1108 : */
1109 : static pg_attribute_always_inline Buffer
1110 122259440 : PinBufferForBlock(Relation rel,
1111 : SMgrRelation smgr,
1112 : char persistence,
1113 : ForkNumber forkNum,
1114 : BlockNumber blockNum,
1115 : BufferAccessStrategy strategy,
1116 : bool *foundPtr)
1117 : {
1118 : BufferDesc *bufHdr;
1119 : IOContext io_context;
1120 : IOObject io_object;
1121 :
1122 : Assert(blockNum != P_NEW);
1123 :
1124 : /* Persistence should be set before */
1125 : Assert((persistence == RELPERSISTENCE_TEMP ||
1126 : persistence == RELPERSISTENCE_PERMANENT ||
1127 : persistence == RELPERSISTENCE_UNLOGGED));
1128 :
1129 122259440 : if (persistence == RELPERSISTENCE_TEMP)
1130 : {
1131 2554160 : io_context = IOCONTEXT_NORMAL;
1132 2554160 : io_object = IOOBJECT_TEMP_RELATION;
1133 : }
1134 : else
1135 : {
1136 119705280 : io_context = IOContextForStrategy(strategy);
1137 119705280 : io_object = IOOBJECT_RELATION;
1138 : }
1139 :
1140 : TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
1141 : smgr->smgr_rlocator.locator.spcOid,
1142 : smgr->smgr_rlocator.locator.dbOid,
1143 : smgr->smgr_rlocator.locator.relNumber,
1144 : smgr->smgr_rlocator.backend);
1145 :
1146 122259440 : if (persistence == RELPERSISTENCE_TEMP)
1147 : {
1148 2554160 : bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
1149 2554148 : if (*foundPtr)
1150 2537378 : pgBufferUsage.local_blks_hit++;
1151 : }
1152 : else
1153 : {
1154 119705280 : bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
1155 : strategy, foundPtr, io_context);
1156 119705280 : if (*foundPtr)
1157 116375358 : pgBufferUsage.shared_blks_hit++;
1158 : }
1159 122259428 : if (rel)
1160 : {
1161 : /*
1162 : * While pgBufferUsage's "read" counter isn't bumped unless we reach
1163 : * WaitReadBuffers() (so, not for hits, and not for buffers that are
1164 : * zeroed instead), the per-relation stats always count them.
1165 : */
1166 110463368 : pgstat_count_buffer_read(rel);
1167 110463368 : if (*foundPtr)
1168 108021054 : pgstat_count_buffer_hit(rel);
1169 : }
1170 122259428 : if (*foundPtr)
1171 : {
1172 118912736 : pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
1173 118912736 : if (VacuumCostActive)
1174 5306434 : VacuumCostBalance += VacuumCostPageHit;
1175 :
1176 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1177 : smgr->smgr_rlocator.locator.spcOid,
1178 : smgr->smgr_rlocator.locator.dbOid,
1179 : smgr->smgr_rlocator.locator.relNumber,
1180 : smgr->smgr_rlocator.backend,
1181 : true);
1182 : }
1183 :
1184 122259428 : return BufferDescriptorGetBuffer(bufHdr);
1185 : }
1186 :
1187 : /*
1188 : * ReadBuffer_common -- common logic for all ReadBuffer variants
1189 : *
1190 : * smgr is required, rel is optional unless using P_NEW.
1191 : */
1192 : static pg_attribute_always_inline Buffer
1193 114168818 : ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
1194 : ForkNumber forkNum,
1195 : BlockNumber blockNum, ReadBufferMode mode,
1196 : BufferAccessStrategy strategy)
1197 : {
1198 : ReadBuffersOperation operation;
1199 : Buffer buffer;
1200 : int flags;
1201 : char persistence;
1202 :
1203 : /*
1204 : * Backward compatibility path, most code should use ExtendBufferedRel()
1205 : * instead, as acquiring the extension lock inside ExtendBufferedRel()
1206 : * scales a lot better.
1207 : */
1208 114168818 : if (unlikely(blockNum == P_NEW))
1209 : {
1210 520 : uint32 flags = EB_SKIP_EXTENSION_LOCK;
1211 :
1212 : /*
1213 : * Since no-one else can be looking at the page contents yet, there is
1214 : * no difference between an exclusive lock and a cleanup-strength
1215 : * lock.
1216 : */
1217 520 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1218 0 : flags |= EB_LOCK_FIRST;
1219 :
1220 520 : return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
1221 : }
1222 :
1223 114168298 : if (rel)
1224 102832592 : persistence = rel->rd_rel->relpersistence;
1225 : else
1226 11335706 : persistence = smgr_persistence;
1227 :
1228 114168298 : if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
1229 : mode == RBM_ZERO_AND_LOCK))
1230 : {
1231 : bool found;
1232 :
1233 622878 : buffer = PinBufferForBlock(rel, smgr, persistence,
1234 : forkNum, blockNum, strategy, &found);
1235 622878 : ZeroAndLockBuffer(buffer, mode, found);
1236 622878 : return buffer;
1237 : }
1238 :
1239 : /*
1240 : * Signal that we are going to immediately wait. If we're immediately
1241 : * waiting, there is no benefit in actually executing the IO
1242 : * asynchronously, it would just add dispatch overhead.
1243 : */
1244 113545420 : flags = READ_BUFFERS_SYNCHRONOUSLY;
1245 113545420 : if (mode == RBM_ZERO_ON_ERROR)
1246 2923614 : flags |= READ_BUFFERS_ZERO_ON_ERROR;
1247 113545420 : operation.smgr = smgr;
1248 113545420 : operation.rel = rel;
1249 113545420 : operation.persistence = persistence;
1250 113545420 : operation.forknum = forkNum;
1251 113545420 : operation.strategy = strategy;
1252 113545420 : if (StartReadBuffer(&operation,
1253 : &buffer,
1254 : blockNum,
1255 : flags))
1256 1365450 : WaitReadBuffers(&operation);
1257 :
1258 113545374 : return buffer;
1259 : }
1260 :
1261 : static pg_attribute_always_inline bool
1262 121309986 : StartReadBuffersImpl(ReadBuffersOperation *operation,
1263 : Buffer *buffers,
1264 : BlockNumber blockNum,
1265 : int *nblocks,
1266 : int flags,
1267 : bool allow_forwarding)
1268 : {
1269 121309986 : int actual_nblocks = *nblocks;
1270 121309986 : int maxcombine = 0;
1271 : bool did_start_io;
1272 :
1273 : Assert(*nblocks == 1 || allow_forwarding);
1274 : Assert(*nblocks > 0);
1275 : Assert(*nblocks <= MAX_IO_COMBINE_LIMIT);
1276 :
1277 124107444 : for (int i = 0; i < actual_nblocks; ++i)
1278 : {
1279 : bool found;
1280 :
1281 121639290 : if (allow_forwarding && buffers[i] != InvalidBuffer)
1282 2728 : {
1283 : BufferDesc *bufHdr;
1284 :
1285 : /*
1286 : * This is a buffer that was pinned by an earlier call to
1287 : * StartReadBuffers(), but couldn't be handled in one operation at
1288 : * that time. The operation was split, and the caller has passed
1289 : * an already pinned buffer back to us to handle the rest of the
1290 : * operation. It must continue at the expected block number.
1291 : */
1292 : Assert(BufferGetBlockNumber(buffers[i]) == blockNum + i);
1293 :
1294 : /*
1295 : * It might be an already valid buffer (a hit) that followed the
1296 : * final contiguous block of an earlier I/O (a miss) marking the
1297 : * end of it, or a buffer that some other backend has since made
1298 : * valid by performing the I/O for us, in which case we can handle
1299 : * it as a hit now. It is safe to check for a BM_VALID flag with
1300 : * a relaxed load, because we got a fresh view of it while pinning
1301 : * it in the previous call.
1302 : *
1303 : * On the other hand if we don't see BM_VALID yet, it must be an
1304 : * I/O that was split by the previous call and we need to try to
1305 : * start a new I/O from this block. We're also racing against any
1306 : * other backend that might start the I/O or even manage to mark
1307 : * it BM_VALID after this check, but StartBufferIO() will handle
1308 : * those cases.
1309 : */
1310 2728 : if (BufferIsLocal(buffers[i]))
1311 4 : bufHdr = GetLocalBufferDescriptor(-buffers[i] - 1);
1312 : else
1313 2724 : bufHdr = GetBufferDescriptor(buffers[i] - 1);
1314 : Assert(pg_atomic_read_u32(&bufHdr->state) & BM_TAG_VALID);
1315 2728 : found = pg_atomic_read_u32(&bufHdr->state) & BM_VALID;
1316 : }
1317 : else
1318 : {
1319 121636550 : buffers[i] = PinBufferForBlock(operation->rel,
1320 121636562 : operation->smgr,
1321 121636562 : operation->persistence,
1322 : operation->forknum,
1323 : blockNum + i,
1324 : operation->strategy,
1325 : &found);
1326 : }
1327 :
1328 121639278 : if (found)
1329 : {
1330 : /*
1331 : * We have a hit. If it's the first block in the requested range,
1332 : * we can return it immediately and report that WaitReadBuffers()
1333 : * does not need to be called. If the initial value of *nblocks
1334 : * was larger, the caller will have to call again for the rest.
1335 : */
1336 118841820 : if (i == 0)
1337 : {
1338 118839088 : *nblocks = 1;
1339 :
1340 : #ifdef USE_ASSERT_CHECKING
1341 :
1342 : /*
1343 : * Initialize enough of ReadBuffersOperation to make
1344 : * CheckReadBuffersOperation() work. Outside of assertions
1345 : * that's not necessary when no IO is issued.
1346 : */
1347 : operation->buffers = buffers;
1348 : operation->blocknum = blockNum;
1349 : operation->nblocks = 1;
1350 : operation->nblocks_done = 1;
1351 : CheckReadBuffersOperation(operation, true);
1352 : #endif
1353 118839088 : return false;
1354 : }
1355 :
1356 : /*
1357 : * Otherwise we already have an I/O to perform, but this block
1358 : * can't be included as it is already valid. Split the I/O here.
1359 : * There may or may not be more blocks requiring I/O after this
1360 : * one, we haven't checked, but they can't be contiguous with this
1361 : * one in the way. We'll leave this buffer pinned, forwarding it
1362 : * to the next call, avoiding the need to unpin it here and re-pin
1363 : * it in the next call.
1364 : */
1365 2732 : actual_nblocks = i;
1366 2732 : break;
1367 : }
1368 : else
1369 : {
1370 : /*
1371 : * Check how many blocks we can cover with the same IO. The smgr
1372 : * implementation might e.g. be limited due to a segment boundary.
1373 : */
1374 2797458 : if (i == 0 && actual_nblocks > 1)
1375 : {
1376 66394 : maxcombine = smgrmaxcombine(operation->smgr,
1377 : operation->forknum,
1378 : blockNum);
1379 66394 : if (unlikely(maxcombine < actual_nblocks))
1380 : {
1381 0 : elog(DEBUG2, "limiting nblocks at %u from %u to %u",
1382 : blockNum, actual_nblocks, maxcombine);
1383 0 : actual_nblocks = maxcombine;
1384 : }
1385 : }
1386 : }
1387 : }
1388 2470886 : *nblocks = actual_nblocks;
1389 :
1390 : /* Populate information needed for I/O. */
1391 2470886 : operation->buffers = buffers;
1392 2470886 : operation->blocknum = blockNum;
1393 2470886 : operation->flags = flags;
1394 2470886 : operation->nblocks = actual_nblocks;
1395 2470886 : operation->nblocks_done = 0;
1396 2470886 : pgaio_wref_clear(&operation->io_wref);
1397 :
1398 : /*
1399 : * When using AIO, start the IO in the background. If not, issue prefetch
1400 : * requests if desired by the caller.
1401 : *
1402 : * The reason we have a dedicated path for IOMETHOD_SYNC here is to
1403 : * de-risk the introduction of AIO somewhat. It's a large architectural
1404 : * change, with lots of chances for unanticipated performance effects.
1405 : *
1406 : * Use of IOMETHOD_SYNC already leads to not actually performing IO
1407 : * asynchronously, but without the check here we'd execute IO earlier than
1408 : * we used to. Eventually this IOMETHOD_SYNC specific path should go away.
1409 : */
1410 2470886 : if (io_method != IOMETHOD_SYNC)
1411 : {
1412 : /*
1413 : * Try to start IO asynchronously. It's possible that no IO needs to
1414 : * be started, if another backend already performed the IO.
1415 : *
1416 : * Note that if an IO is started, it might not cover the entire
1417 : * requested range, e.g. because an intermediary block has been read
1418 : * in by another backend. In that case any "trailing" buffers we
1419 : * already pinned above will be "forwarded" by read_stream.c to the
1420 : * next call to StartReadBuffers().
1421 : *
1422 : * This is signalled to the caller by decrementing *nblocks *and*
1423 : * reducing operation->nblocks. The latter is done here, but not below
1424 : * WaitReadBuffers(), as in WaitReadBuffers() we can't "shorten" the
1425 : * overall read size anymore, we need to retry until done in its
1426 : * entirety or until failed.
1427 : */
1428 2468726 : did_start_io = AsyncReadBuffers(operation, nblocks);
1429 :
1430 2468696 : operation->nblocks = *nblocks;
1431 : }
1432 : else
1433 : {
1434 2160 : operation->flags |= READ_BUFFERS_SYNCHRONOUSLY;
1435 :
1436 2160 : if (flags & READ_BUFFERS_ISSUE_ADVICE)
1437 : {
1438 : /*
1439 : * In theory we should only do this if PinBufferForBlock() had to
1440 : * allocate new buffers above. That way, if two calls to
1441 : * StartReadBuffers() were made for the same blocks before
1442 : * WaitReadBuffers(), only the first would issue the advice.
1443 : * That'd be a better simulation of true asynchronous I/O, which
1444 : * would only start the I/O once, but isn't done here for
1445 : * simplicity.
1446 : */
1447 4 : smgrprefetch(operation->smgr,
1448 : operation->forknum,
1449 : blockNum,
1450 : actual_nblocks);
1451 : }
1452 :
1453 : /*
1454 : * Indicate that WaitReadBuffers() should be called. WaitReadBuffers()
1455 : * will initiate the necessary IO.
1456 : */
1457 2160 : did_start_io = true;
1458 : }
1459 :
1460 2470856 : CheckReadBuffersOperation(operation, !did_start_io);
1461 :
1462 2470856 : return did_start_io;
1463 : }
1464 :
1465 : /*
1466 : * Begin reading a range of blocks beginning at blockNum and extending for
1467 : * *nblocks. *nblocks and the buffers array are in/out parameters. On entry,
1468 : * the buffers elements covered by *nblocks must hold either InvalidBuffer or
1469 : * buffers forwarded by an earlier call to StartReadBuffers() that was split
1470 : * and is now being continued. On return, *nblocks holds the number of blocks
1471 : * accepted by this operation. If it is less than the original number then
1472 : * this operation has been split, but buffer elements up to the original
1473 : * requested size may hold forwarded buffers to be used for a continuing
1474 : * operation. The caller must either start a new I/O beginning at the block
1475 : * immediately following the blocks accepted by this call and pass those
1476 : * buffers back in, or release them if it chooses not to. It shouldn't make
1477 : * any other use of or assumptions about forwarded buffers.
1478 : *
1479 : * If false is returned, no I/O is necessary and the buffers covered by
1480 : * *nblocks on exit are valid and ready to be accessed. If true is returned,
1481 : * an I/O has been started, and WaitReadBuffers() must be called with the same
1482 : * operation object before the buffers covered by *nblocks on exit can be
1483 : * accessed. Along with the operation object, the caller-supplied array of
1484 : * buffers must remain valid until WaitReadBuffers() is called, and any
1485 : * forwarded buffers must also be preserved for a continuing call unless
1486 : * they are explicitly released.
1487 : */
1488 : bool
1489 3821560 : StartReadBuffers(ReadBuffersOperation *operation,
1490 : Buffer *buffers,
1491 : BlockNumber blockNum,
1492 : int *nblocks,
1493 : int flags)
1494 : {
1495 3821560 : return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags,
1496 : true /* expect forwarded buffers */ );
1497 : }
1498 :
1499 : /*
1500 : * Single block version of the StartReadBuffers(). This might save a few
1501 : * instructions when called from another translation unit, because it is
1502 : * specialized for nblocks == 1.
1503 : *
1504 : * This version does not support "forwarded" buffers: they cannot be created
1505 : * by reading only one block and *buffer is ignored on entry.
1506 : */
1507 : bool
1508 117488426 : StartReadBuffer(ReadBuffersOperation *operation,
1509 : Buffer *buffer,
1510 : BlockNumber blocknum,
1511 : int flags)
1512 : {
1513 117488426 : int nblocks = 1;
1514 : bool result;
1515 :
1516 117488426 : result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags,
1517 : false /* single block, no forwarding */ );
1518 : Assert(nblocks == 1); /* single block can't be short */
1519 :
1520 117488396 : return result;
1521 : }
1522 :
1523 : /*
1524 : * Perform sanity checks on the ReadBuffersOperation.
1525 : */
1526 : static void
1527 7382094 : CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete)
1528 : {
1529 : #ifdef USE_ASSERT_CHECKING
1530 : Assert(operation->nblocks_done <= operation->nblocks);
1531 : Assert(!is_complete || operation->nblocks == operation->nblocks_done);
1532 :
1533 : for (int i = 0; i < operation->nblocks; i++)
1534 : {
1535 : Buffer buffer = operation->buffers[i];
1536 : BufferDesc *buf_hdr = BufferIsLocal(buffer) ?
1537 : GetLocalBufferDescriptor(-buffer - 1) :
1538 : GetBufferDescriptor(buffer - 1);
1539 :
1540 : Assert(BufferGetBlockNumber(buffer) == operation->blocknum + i);
1541 : Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_TAG_VALID);
1542 :
1543 : if (i < operation->nblocks_done)
1544 : Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_VALID);
1545 : }
1546 : #endif
1547 7382094 : }
1548 :
1549 : /* helper for ReadBuffersCanStartIO(), to avoid repetition */
1550 : static inline bool
1551 2797494 : ReadBuffersCanStartIOOnce(Buffer buffer, bool nowait)
1552 : {
1553 2797494 : if (BufferIsLocal(buffer))
1554 16722 : return StartLocalBufferIO(GetLocalBufferDescriptor(-buffer - 1),
1555 : true, nowait);
1556 : else
1557 2780772 : return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
1558 : }
1559 :
1560 : /*
1561 : * Helper for AsyncReadBuffers that tries to get the buffer ready for IO.
1562 : */
1563 : static inline bool
1564 2797494 : ReadBuffersCanStartIO(Buffer buffer, bool nowait)
1565 : {
1566 : /*
1567 : * If this backend currently has staged IO, we need to submit the pending
1568 : * IO before waiting for the right to issue IO, to avoid the potential for
1569 : * deadlocks (and, more commonly, unnecessary delays for other backends).
1570 : */
1571 2797494 : if (!nowait && pgaio_have_staged())
1572 : {
1573 1098 : if (ReadBuffersCanStartIOOnce(buffer, true))
1574 1098 : return true;
1575 :
1576 : /*
1577 : * Unfortunately StartBufferIO() returning false doesn't allow to
1578 : * distinguish between the buffer already being valid and IO already
1579 : * being in progress. Since IO already being in progress is quite
1580 : * rare, this approach seems fine.
1581 : */
1582 0 : pgaio_submit_staged();
1583 : }
1584 :
1585 2796396 : return ReadBuffersCanStartIOOnce(buffer, nowait);
1586 : }
1587 :
1588 : /*
1589 : * Helper for WaitReadBuffers() that processes the results of a readv
1590 : * operation, raising an error if necessary.
1591 : */
1592 : static void
1593 2454578 : ProcessReadBuffersResult(ReadBuffersOperation *operation)
1594 : {
1595 2454578 : PgAioReturn *aio_ret = &operation->io_return;
1596 2454578 : PgAioResultStatus rs = aio_ret->result.status;
1597 2454578 : int newly_read_blocks = 0;
1598 :
1599 : Assert(pgaio_wref_valid(&operation->io_wref));
1600 : Assert(aio_ret->result.status != PGAIO_RS_UNKNOWN);
1601 :
1602 : /*
1603 : * SMGR reports the number of blocks successfully read as the result of
1604 : * the IO operation. Thus we can simply add that to ->nblocks_done.
1605 : */
1606 :
1607 2454578 : if (likely(rs != PGAIO_RS_ERROR))
1608 2454520 : newly_read_blocks = aio_ret->result.result;
1609 :
1610 2454578 : if (rs == PGAIO_RS_ERROR || rs == PGAIO_RS_WARNING)
1611 90 : pgaio_result_report(aio_ret->result, &aio_ret->target_data,
1612 : rs == PGAIO_RS_ERROR ? ERROR : WARNING);
1613 2454488 : else if (aio_ret->result.status == PGAIO_RS_PARTIAL)
1614 : {
1615 : /*
1616 : * We'll retry, so we just emit a debug message to the server log (or
1617 : * not even that in prod scenarios).
1618 : */
1619 20 : pgaio_result_report(aio_ret->result, &aio_ret->target_data, DEBUG1);
1620 20 : elog(DEBUG3, "partial read, will retry");
1621 : }
1622 :
1623 : Assert(newly_read_blocks > 0);
1624 : Assert(newly_read_blocks <= MAX_IO_COMBINE_LIMIT);
1625 :
1626 2454520 : operation->nblocks_done += newly_read_blocks;
1627 :
1628 : Assert(operation->nblocks_done <= operation->nblocks);
1629 2454520 : }
1630 :
1631 : void
1632 2454558 : WaitReadBuffers(ReadBuffersOperation *operation)
1633 : {
1634 2454558 : PgAioReturn *aio_ret = &operation->io_return;
1635 : IOContext io_context;
1636 : IOObject io_object;
1637 :
1638 2454558 : if (operation->persistence == RELPERSISTENCE_TEMP)
1639 : {
1640 2968 : io_context = IOCONTEXT_NORMAL;
1641 2968 : io_object = IOOBJECT_TEMP_RELATION;
1642 : }
1643 : else
1644 : {
1645 2451590 : io_context = IOContextForStrategy(operation->strategy);
1646 2451590 : io_object = IOOBJECT_RELATION;
1647 : }
1648 :
1649 : /*
1650 : * If we get here without an IO operation having been issued, the
1651 : * io_method == IOMETHOD_SYNC path must have been used. Otherwise the
1652 : * caller should not have called WaitReadBuffers().
1653 : *
1654 : * In the case of IOMETHOD_SYNC, we start - as we used to before the
1655 : * introducing of AIO - the IO in WaitReadBuffers(). This is done as part
1656 : * of the retry logic below, no extra code is required.
1657 : *
1658 : * This path is expected to eventually go away.
1659 : */
1660 2454558 : if (!pgaio_wref_valid(&operation->io_wref) && io_method != IOMETHOD_SYNC)
1661 0 : elog(ERROR, "waiting for read operation that didn't read");
1662 :
1663 : /*
1664 : * To handle partial reads, and IOMETHOD_SYNC, we re-issue IO until we're
1665 : * done. We may need multiple retries, not just because we could get
1666 : * multiple partial reads, but also because some of the remaining
1667 : * to-be-read buffers may have been read in by other backends, limiting
1668 : * the IO size.
1669 : */
1670 : while (true)
1671 2180 : {
1672 : int ignored_nblocks_progress;
1673 :
1674 2456738 : CheckReadBuffersOperation(operation, false);
1675 :
1676 : /*
1677 : * If there is an IO associated with the operation, we may need to
1678 : * wait for it.
1679 : */
1680 2456738 : if (pgaio_wref_valid(&operation->io_wref))
1681 : {
1682 : /*
1683 : * Track the time spent waiting for the IO to complete. As
1684 : * tracking a wait even if we don't actually need to wait
1685 : *
1686 : * a) is not cheap, due to the timestamping overhead
1687 : *
1688 : * b) reports some time as waiting, even if we never waited
1689 : *
1690 : * we first check if we already know the IO is complete.
1691 : */
1692 2454578 : if (aio_ret->result.status == PGAIO_RS_UNKNOWN &&
1693 1074490 : !pgaio_wref_check_done(&operation->io_wref))
1694 : {
1695 371408 : instr_time io_start = pgstat_prepare_io_time(track_io_timing);
1696 :
1697 371408 : pgaio_wref_wait(&operation->io_wref);
1698 :
1699 : /*
1700 : * The IO operation itself was already counted earlier, in
1701 : * AsyncReadBuffers(), this just accounts for the wait time.
1702 : */
1703 371408 : pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
1704 : io_start, 0, 0);
1705 : }
1706 : else
1707 : {
1708 : Assert(pgaio_wref_check_done(&operation->io_wref));
1709 : }
1710 :
1711 : /*
1712 : * We now are sure the IO completed. Check the results. This
1713 : * includes reporting on errors if there were any.
1714 : */
1715 2454578 : ProcessReadBuffersResult(operation);
1716 : }
1717 :
1718 : /*
1719 : * Most of the time, the one IO we already started, will read in
1720 : * everything. But we need to deal with partial reads and buffers not
1721 : * needing IO anymore.
1722 : */
1723 2456680 : if (operation->nblocks_done == operation->nblocks)
1724 2454500 : break;
1725 :
1726 2180 : CHECK_FOR_INTERRUPTS();
1727 :
1728 : /*
1729 : * This may only complete the IO partially, either because some
1730 : * buffers were already valid, or because of a partial read.
1731 : *
1732 : * NB: In contrast to after the AsyncReadBuffers() call in
1733 : * StartReadBuffers(), we do *not* reduce
1734 : * ReadBuffersOperation->nblocks here, callers expect the full
1735 : * operation to be completed at this point (as more operations may
1736 : * have been queued).
1737 : */
1738 2180 : AsyncReadBuffers(operation, &ignored_nblocks_progress);
1739 : }
1740 :
1741 2454500 : CheckReadBuffersOperation(operation, true);
1742 :
1743 : /* NB: READ_DONE tracepoint was already executed in completion callback */
1744 2454500 : }
1745 :
1746 : /*
1747 : * Initiate IO for the ReadBuffersOperation
1748 : *
1749 : * This function only starts a single IO at a time. The size of the IO may be
1750 : * limited to below the to-be-read blocks, if one of the buffers has
1751 : * concurrently been read in. If the first to-be-read buffer is already valid,
1752 : * no IO will be issued.
1753 : *
1754 : * To support retries after partial reads, the first operation->nblocks_done
1755 : * buffers are skipped.
1756 : *
1757 : * On return *nblocks_progress is updated to reflect the number of buffers
1758 : * affected by the call. If the first buffer is valid, *nblocks_progress is
1759 : * set to 1 and operation->nblocks_done is incremented.
1760 : *
1761 : * Returns true if IO was initiated, false if no IO was necessary.
1762 : */
1763 : static bool
1764 2470906 : AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
1765 : {
1766 2470906 : Buffer *buffers = &operation->buffers[0];
1767 2470906 : int flags = operation->flags;
1768 2470906 : BlockNumber blocknum = operation->blocknum;
1769 2470906 : ForkNumber forknum = operation->forknum;
1770 2470906 : char persistence = operation->persistence;
1771 2470906 : int16 nblocks_done = operation->nblocks_done;
1772 2470906 : Buffer *io_buffers = &operation->buffers[nblocks_done];
1773 2470906 : int io_buffers_len = 0;
1774 : PgAioHandle *ioh;
1775 2470906 : uint32 ioh_flags = 0;
1776 : void *io_pages[MAX_IO_COMBINE_LIMIT];
1777 : IOContext io_context;
1778 : IOObject io_object;
1779 : bool did_start_io;
1780 :
1781 : /*
1782 : * When this IO is executed synchronously, either because the caller will
1783 : * immediately block waiting for the IO or because IOMETHOD_SYNC is used,
1784 : * the AIO subsystem needs to know.
1785 : */
1786 2470906 : if (flags & READ_BUFFERS_SYNCHRONOUSLY)
1787 1375340 : ioh_flags |= PGAIO_HF_SYNCHRONOUS;
1788 :
1789 2470906 : if (persistence == RELPERSISTENCE_TEMP)
1790 : {
1791 3556 : io_context = IOCONTEXT_NORMAL;
1792 3556 : io_object = IOOBJECT_TEMP_RELATION;
1793 3556 : ioh_flags |= PGAIO_HF_REFERENCES_LOCAL;
1794 : }
1795 : else
1796 : {
1797 2467350 : io_context = IOContextForStrategy(operation->strategy);
1798 2467350 : io_object = IOOBJECT_RELATION;
1799 : }
1800 :
1801 : /*
1802 : * If zero_damaged_pages is enabled, add the READ_BUFFERS_ZERO_ON_ERROR
1803 : * flag. The reason for that is that, hopefully, zero_damaged_pages isn't
1804 : * set globally, but on a per-session basis. The completion callback,
1805 : * which may be run in other processes, e.g. in IO workers, may have a
1806 : * different value of the zero_damaged_pages GUC.
1807 : *
1808 : * XXX: We probably should eventually use a different flag for
1809 : * zero_damaged_pages, so we can report different log levels / error codes
1810 : * for zero_damaged_pages and ZERO_ON_ERROR.
1811 : */
1812 2470906 : if (zero_damaged_pages)
1813 32 : flags |= READ_BUFFERS_ZERO_ON_ERROR;
1814 :
1815 : /*
1816 : * For the same reason as with zero_damaged_pages we need to use this
1817 : * backend's ignore_checksum_failure value.
1818 : */
1819 2470906 : if (ignore_checksum_failure)
1820 16 : flags |= READ_BUFFERS_IGNORE_CHECKSUM_FAILURES;
1821 :
1822 :
1823 : /*
1824 : * To be allowed to report stats in the local completion callback we need
1825 : * to prepare to report stats now. This ensures we can safely report the
1826 : * checksum failure even in a critical section.
1827 : */
1828 2470906 : pgstat_prepare_report_checksum_failure(operation->smgr->smgr_rlocator.locator.dbOid);
1829 :
1830 : /*
1831 : * Get IO handle before ReadBuffersCanStartIO(), as pgaio_io_acquire()
1832 : * might block, which we don't want after setting IO_IN_PROGRESS.
1833 : *
1834 : * If we need to wait for IO before we can get a handle, submit
1835 : * already-staged IO first, so that other backends don't need to wait.
1836 : * There wouldn't be a deadlock risk, as pgaio_io_acquire() just needs to
1837 : * wait for already submitted IO, which doesn't require additional locks,
1838 : * but it could still cause undesirable waits.
1839 : *
1840 : * A secondary benefit is that this would allow us to measure the time in
1841 : * pgaio_io_acquire() without causing undue timer overhead in the common,
1842 : * non-blocking, case. However, currently the pgstats infrastructure
1843 : * doesn't really allow that, as it a) asserts that an operation can't
1844 : * have time without operations b) doesn't have an API to report
1845 : * "accumulated" time.
1846 : */
1847 2470906 : ioh = pgaio_io_acquire_nb(CurrentResourceOwner, &operation->io_return);
1848 2470906 : if (unlikely(!ioh))
1849 : {
1850 6392 : pgaio_submit_staged();
1851 :
1852 6392 : ioh = pgaio_io_acquire(CurrentResourceOwner, &operation->io_return);
1853 : }
1854 :
1855 : /*
1856 : * Check if we can start IO on the first to-be-read buffer.
1857 : *
1858 : * If an I/O is already in progress in another backend, we want to wait
1859 : * for the outcome: either done, or something went wrong and we will
1860 : * retry.
1861 : */
1862 2470906 : if (!ReadBuffersCanStartIO(buffers[nblocks_done], false))
1863 : {
1864 : /*
1865 : * Someone else has already completed this block, we're done.
1866 : *
1867 : * When IO is necessary, ->nblocks_done is updated in
1868 : * ProcessReadBuffersResult(), but that is not called if no IO is
1869 : * necessary. Thus update here.
1870 : */
1871 15704 : operation->nblocks_done += 1;
1872 15704 : *nblocks_progress = 1;
1873 :
1874 15704 : pgaio_io_release(ioh);
1875 15704 : pgaio_wref_clear(&operation->io_wref);
1876 15704 : did_start_io = false;
1877 :
1878 : /*
1879 : * Report and track this as a 'hit' for this backend, even though it
1880 : * must have started out as a miss in PinBufferForBlock(). The other
1881 : * backend will track this as a 'read'.
1882 : */
1883 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
1884 : operation->smgr->smgr_rlocator.locator.spcOid,
1885 : operation->smgr->smgr_rlocator.locator.dbOid,
1886 : operation->smgr->smgr_rlocator.locator.relNumber,
1887 : operation->smgr->smgr_rlocator.backend,
1888 : true);
1889 :
1890 15704 : if (persistence == RELPERSISTENCE_TEMP)
1891 0 : pgBufferUsage.local_blks_hit += 1;
1892 : else
1893 15704 : pgBufferUsage.shared_blks_hit += 1;
1894 :
1895 15704 : if (operation->rel)
1896 15704 : pgstat_count_buffer_hit(operation->rel);
1897 :
1898 15704 : pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
1899 :
1900 15704 : if (VacuumCostActive)
1901 264 : VacuumCostBalance += VacuumCostPageHit;
1902 : }
1903 : else
1904 : {
1905 : instr_time io_start;
1906 :
1907 : /* We found a buffer that we need to read in. */
1908 : Assert(io_buffers[0] == buffers[nblocks_done]);
1909 2455202 : io_pages[0] = BufferGetBlock(buffers[nblocks_done]);
1910 2455202 : io_buffers_len = 1;
1911 :
1912 : /*
1913 : * How many neighboring-on-disk blocks can we scatter-read into other
1914 : * buffers at the same time? In this case we don't wait if we see an
1915 : * I/O already in progress. We already set BM_IO_IN_PROGRESS for the
1916 : * head block, so we should get on with that I/O as soon as possible.
1917 : */
1918 2781790 : for (int i = nblocks_done + 1; i < operation->nblocks; i++)
1919 : {
1920 326588 : if (!ReadBuffersCanStartIO(buffers[i], true))
1921 0 : break;
1922 : /* Must be consecutive block numbers. */
1923 : Assert(BufferGetBlockNumber(buffers[i - 1]) ==
1924 : BufferGetBlockNumber(buffers[i]) - 1);
1925 : Assert(io_buffers[io_buffers_len] == buffers[i]);
1926 :
1927 326588 : io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
1928 : }
1929 :
1930 : /* get a reference to wait for in WaitReadBuffers() */
1931 2455202 : pgaio_io_get_wref(ioh, &operation->io_wref);
1932 :
1933 : /* provide the list of buffers to the completion callbacks */
1934 2455202 : pgaio_io_set_handle_data_32(ioh, (uint32 *) io_buffers, io_buffers_len);
1935 :
1936 2455202 : pgaio_io_register_callbacks(ioh,
1937 : persistence == RELPERSISTENCE_TEMP ?
1938 : PGAIO_HCB_LOCAL_BUFFER_READV :
1939 : PGAIO_HCB_SHARED_BUFFER_READV,
1940 : flags);
1941 :
1942 2455202 : pgaio_io_set_flag(ioh, ioh_flags);
1943 :
1944 : /* ---
1945 : * Even though we're trying to issue IO asynchronously, track the time
1946 : * in smgrstartreadv():
1947 : * - if io_method == IOMETHOD_SYNC, we will always perform the IO
1948 : * immediately
1949 : * - the io method might not support the IO (e.g. worker IO for a temp
1950 : * table)
1951 : * ---
1952 : */
1953 2455202 : io_start = pgstat_prepare_io_time(track_io_timing);
1954 2455202 : smgrstartreadv(ioh, operation->smgr, forknum,
1955 : blocknum + nblocks_done,
1956 : io_pages, io_buffers_len);
1957 2455172 : pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
1958 2455172 : io_start, 1, io_buffers_len * BLCKSZ);
1959 :
1960 2455172 : if (persistence == RELPERSISTENCE_TEMP)
1961 3556 : pgBufferUsage.local_blks_read += io_buffers_len;
1962 : else
1963 2451616 : pgBufferUsage.shared_blks_read += io_buffers_len;
1964 :
1965 : /*
1966 : * Track vacuum cost when issuing IO, not after waiting for it.
1967 : * Otherwise we could end up issuing a lot of IO in a short timespan,
1968 : * despite a low cost limit.
1969 : */
1970 2455172 : if (VacuumCostActive)
1971 34536 : VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
1972 :
1973 2455172 : *nblocks_progress = io_buffers_len;
1974 2455172 : did_start_io = true;
1975 : }
1976 :
1977 2470876 : return did_start_io;
1978 : }
1979 :
1980 : /*
1981 : * BufferAlloc -- subroutine for PinBufferForBlock. Handles lookup of a shared
1982 : * buffer. If no buffer exists already, selects a replacement victim and
1983 : * evicts the old page, but does NOT read in new page.
1984 : *
1985 : * "strategy" can be a buffer replacement strategy object, or NULL for
1986 : * the default strategy. The selected buffer's usage_count is advanced when
1987 : * using the default strategy, but otherwise possibly not (see PinBuffer).
1988 : *
1989 : * The returned buffer is pinned and is already marked as holding the
1990 : * desired page. If it already did have the desired page, *foundPtr is
1991 : * set true. Otherwise, *foundPtr is set false.
1992 : *
1993 : * io_context is passed as an output parameter to avoid calling
1994 : * IOContextForStrategy() when there is a shared buffers hit and no IO
1995 : * statistics need be captured.
1996 : *
1997 : * No locks are held either at entry or exit.
1998 : */
1999 : static pg_attribute_always_inline BufferDesc *
2000 119705280 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
2001 : BlockNumber blockNum,
2002 : BufferAccessStrategy strategy,
2003 : bool *foundPtr, IOContext io_context)
2004 : {
2005 : BufferTag newTag; /* identity of requested block */
2006 : uint32 newHash; /* hash value for newTag */
2007 : LWLock *newPartitionLock; /* buffer partition lock for it */
2008 : int existing_buf_id;
2009 : Buffer victim_buffer;
2010 : BufferDesc *victim_buf_hdr;
2011 : uint32 victim_buf_state;
2012 :
2013 : /* Make sure we will have room to remember the buffer pin */
2014 119705280 : ResourceOwnerEnlarge(CurrentResourceOwner);
2015 119705280 : ReservePrivateRefCountEntry();
2016 :
2017 : /* create a tag so we can lookup the buffer */
2018 119705280 : InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
2019 :
2020 : /* determine its hash code and partition lock ID */
2021 119705280 : newHash = BufTableHashCode(&newTag);
2022 119705280 : newPartitionLock = BufMappingPartitionLock(newHash);
2023 :
2024 : /* see if the block is in the buffer pool already */
2025 119705280 : LWLockAcquire(newPartitionLock, LW_SHARED);
2026 119705280 : existing_buf_id = BufTableLookup(&newTag, newHash);
2027 119705280 : if (existing_buf_id >= 0)
2028 : {
2029 : BufferDesc *buf;
2030 : bool valid;
2031 :
2032 : /*
2033 : * Found it. Now, pin the buffer so no one can steal it from the
2034 : * buffer pool, and check to see if the correct data has been loaded
2035 : * into the buffer.
2036 : */
2037 116388526 : buf = GetBufferDescriptor(existing_buf_id);
2038 :
2039 116388526 : valid = PinBuffer(buf, strategy);
2040 :
2041 : /* Can release the mapping lock as soon as we've pinned it */
2042 116388526 : LWLockRelease(newPartitionLock);
2043 :
2044 116388526 : *foundPtr = true;
2045 :
2046 116388526 : if (!valid)
2047 : {
2048 : /*
2049 : * We can only get here if (a) someone else is still reading in
2050 : * the page, (b) a previous read attempt failed, or (c) someone
2051 : * called StartReadBuffers() but not yet WaitReadBuffers().
2052 : */
2053 13826 : *foundPtr = false;
2054 : }
2055 :
2056 116388526 : return buf;
2057 : }
2058 :
2059 : /*
2060 : * Didn't find it in the buffer pool. We'll have to initialize a new
2061 : * buffer. Remember to unlock the mapping lock while doing the work.
2062 : */
2063 3316754 : LWLockRelease(newPartitionLock);
2064 :
2065 : /*
2066 : * Acquire a victim buffer. Somebody else might try to do the same, we
2067 : * don't hold any conflicting locks. If so we'll have to undo our work
2068 : * later.
2069 : */
2070 3316754 : victim_buffer = GetVictimBuffer(strategy, io_context);
2071 3316754 : victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
2072 :
2073 : /*
2074 : * Try to make a hashtable entry for the buffer under its new tag. If
2075 : * somebody else inserted another buffer for the tag, we'll release the
2076 : * victim buffer we acquired and use the already inserted one.
2077 : */
2078 3316754 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
2079 3316754 : existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
2080 3316754 : if (existing_buf_id >= 0)
2081 : {
2082 : BufferDesc *existing_buf_hdr;
2083 : bool valid;
2084 :
2085 : /*
2086 : * Got a collision. Someone has already done what we were about to do.
2087 : * We'll just handle this as if it were found in the buffer pool in
2088 : * the first place. First, give up the buffer we were planning to
2089 : * use.
2090 : *
2091 : * We could do this after releasing the partition lock, but then we'd
2092 : * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
2093 : * before acquiring the lock, for the rare case of such a collision.
2094 : */
2095 2632 : UnpinBuffer(victim_buf_hdr);
2096 :
2097 : /*
2098 : * The victim buffer we acquired previously is clean and unused, let
2099 : * it be found again quickly
2100 : */
2101 2632 : StrategyFreeBuffer(victim_buf_hdr);
2102 :
2103 : /* remaining code should match code at top of routine */
2104 :
2105 2632 : existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
2106 :
2107 2632 : valid = PinBuffer(existing_buf_hdr, strategy);
2108 :
2109 : /* Can release the mapping lock as soon as we've pinned it */
2110 2632 : LWLockRelease(newPartitionLock);
2111 :
2112 2632 : *foundPtr = true;
2113 :
2114 2632 : if (!valid)
2115 : {
2116 : /*
2117 : * We can only get here if (a) someone else is still reading in
2118 : * the page, (b) a previous read attempt failed, or (c) someone
2119 : * called StartReadBuffers() but not yet WaitReadBuffers().
2120 : */
2121 1974 : *foundPtr = false;
2122 : }
2123 :
2124 2632 : return existing_buf_hdr;
2125 : }
2126 :
2127 : /*
2128 : * Need to lock the buffer header too in order to change its tag.
2129 : */
2130 3314122 : victim_buf_state = LockBufHdr(victim_buf_hdr);
2131 :
2132 : /* some sanity checks while we hold the buffer header lock */
2133 : Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
2134 : Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
2135 :
2136 3314122 : victim_buf_hdr->tag = newTag;
2137 :
2138 : /*
2139 : * Make sure BM_PERMANENT is set for buffers that must be written at every
2140 : * checkpoint. Unlogged buffers only need to be written at shutdown
2141 : * checkpoints, except for their "init" forks, which need to be treated
2142 : * just like permanent relations.
2143 : */
2144 3314122 : victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2145 3314122 : if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
2146 3313442 : victim_buf_state |= BM_PERMANENT;
2147 :
2148 3314122 : UnlockBufHdr(victim_buf_hdr, victim_buf_state);
2149 :
2150 3314122 : LWLockRelease(newPartitionLock);
2151 :
2152 : /*
2153 : * Buffer contents are currently invalid.
2154 : */
2155 3314122 : *foundPtr = false;
2156 :
2157 3314122 : return victim_buf_hdr;
2158 : }
2159 :
2160 : /*
2161 : * InvalidateBuffer -- mark a shared buffer invalid and return it to the
2162 : * freelist.
2163 : *
2164 : * The buffer header spinlock must be held at entry. We drop it before
2165 : * returning. (This is sane because the caller must have locked the
2166 : * buffer in order to be sure it should be dropped.)
2167 : *
2168 : * This is used only in contexts such as dropping a relation. We assume
2169 : * that no other backend could possibly be interested in using the page,
2170 : * so the only reason the buffer might be pinned is if someone else is
2171 : * trying to write it out. We have to let them finish before we can
2172 : * reclaim the buffer.
2173 : *
2174 : * The buffer could get reclaimed by someone else while we are waiting
2175 : * to acquire the necessary locks; if so, don't mess it up.
2176 : */
2177 : static void
2178 209738 : InvalidateBuffer(BufferDesc *buf)
2179 : {
2180 : BufferTag oldTag;
2181 : uint32 oldHash; /* hash value for oldTag */
2182 : LWLock *oldPartitionLock; /* buffer partition lock for it */
2183 : uint32 oldFlags;
2184 : uint32 buf_state;
2185 :
2186 : /* Save the original buffer tag before dropping the spinlock */
2187 209738 : oldTag = buf->tag;
2188 :
2189 209738 : buf_state = pg_atomic_read_u32(&buf->state);
2190 : Assert(buf_state & BM_LOCKED);
2191 209738 : UnlockBufHdr(buf, buf_state);
2192 :
2193 : /*
2194 : * Need to compute the old tag's hashcode and partition lock ID. XXX is it
2195 : * worth storing the hashcode in BufferDesc so we need not recompute it
2196 : * here? Probably not.
2197 : */
2198 209738 : oldHash = BufTableHashCode(&oldTag);
2199 209738 : oldPartitionLock = BufMappingPartitionLock(oldHash);
2200 :
2201 209750 : retry:
2202 :
2203 : /*
2204 : * Acquire exclusive mapping lock in preparation for changing the buffer's
2205 : * association.
2206 : */
2207 209750 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
2208 :
2209 : /* Re-lock the buffer header */
2210 209750 : buf_state = LockBufHdr(buf);
2211 :
2212 : /* If it's changed while we were waiting for lock, do nothing */
2213 209750 : if (!BufferTagsEqual(&buf->tag, &oldTag))
2214 : {
2215 10 : UnlockBufHdr(buf, buf_state);
2216 10 : LWLockRelease(oldPartitionLock);
2217 10 : return;
2218 : }
2219 :
2220 : /*
2221 : * We assume the reason for it to be pinned is that either we were
2222 : * asynchronously reading the page in before erroring out or someone else
2223 : * is flushing the page out. Wait for the IO to finish. (This could be
2224 : * an infinite loop if the refcount is messed up... it would be nice to
2225 : * time out after awhile, but there seems no way to be sure how many loops
2226 : * may be needed. Note that if the other guy has pinned the buffer but
2227 : * not yet done StartBufferIO, WaitIO will fall through and we'll
2228 : * effectively be busy-looping here.)
2229 : */
2230 209740 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
2231 : {
2232 12 : UnlockBufHdr(buf, buf_state);
2233 12 : LWLockRelease(oldPartitionLock);
2234 : /* safety check: should definitely not be our *own* pin */
2235 12 : if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
2236 0 : elog(ERROR, "buffer is pinned in InvalidateBuffer");
2237 12 : WaitIO(buf);
2238 12 : goto retry;
2239 : }
2240 :
2241 : /*
2242 : * Clear out the buffer's tag and flags. We must do this to ensure that
2243 : * linear scans of the buffer array don't think the buffer is valid.
2244 : */
2245 209728 : oldFlags = buf_state & BUF_FLAG_MASK;
2246 209728 : ClearBufferTag(&buf->tag);
2247 209728 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
2248 209728 : UnlockBufHdr(buf, buf_state);
2249 :
2250 : /*
2251 : * Remove the buffer from the lookup hashtable, if it was in there.
2252 : */
2253 209728 : if (oldFlags & BM_TAG_VALID)
2254 209728 : BufTableDelete(&oldTag, oldHash);
2255 :
2256 : /*
2257 : * Done with mapping lock.
2258 : */
2259 209728 : LWLockRelease(oldPartitionLock);
2260 :
2261 : /*
2262 : * Insert the buffer at the head of the list of free buffers.
2263 : */
2264 209728 : StrategyFreeBuffer(buf);
2265 : }
2266 :
2267 : /*
2268 : * Helper routine for GetVictimBuffer()
2269 : *
2270 : * Needs to be called on a buffer with a valid tag, pinned, but without the
2271 : * buffer header spinlock held.
2272 : *
2273 : * Returns true if the buffer can be reused, in which case the buffer is only
2274 : * pinned by this backend and marked as invalid, false otherwise.
2275 : */
2276 : static bool
2277 2327948 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
2278 : {
2279 : uint32 buf_state;
2280 : uint32 hash;
2281 : LWLock *partition_lock;
2282 : BufferTag tag;
2283 :
2284 : Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
2285 :
2286 : /* have buffer pinned, so it's safe to read tag without lock */
2287 2327948 : tag = buf_hdr->tag;
2288 :
2289 2327948 : hash = BufTableHashCode(&tag);
2290 2327948 : partition_lock = BufMappingPartitionLock(hash);
2291 :
2292 2327948 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
2293 :
2294 : /* lock the buffer header */
2295 2327948 : buf_state = LockBufHdr(buf_hdr);
2296 :
2297 : /*
2298 : * We have the buffer pinned nobody else should have been able to unset
2299 : * this concurrently.
2300 : */
2301 : Assert(buf_state & BM_TAG_VALID);
2302 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2303 : Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
2304 :
2305 : /*
2306 : * If somebody else pinned the buffer since, or even worse, dirtied it,
2307 : * give up on this buffer: It's clearly in use.
2308 : */
2309 2327948 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
2310 : {
2311 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2312 :
2313 734 : UnlockBufHdr(buf_hdr, buf_state);
2314 734 : LWLockRelease(partition_lock);
2315 :
2316 734 : return false;
2317 : }
2318 :
2319 : /*
2320 : * Clear out the buffer's tag and flags and usagecount. This is not
2321 : * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
2322 : * doing anything with the buffer. But currently it's beneficial, as the
2323 : * cheaper pre-check for several linear scans of shared buffers use the
2324 : * tag (see e.g. FlushDatabaseBuffers()).
2325 : */
2326 2327214 : ClearBufferTag(&buf_hdr->tag);
2327 2327214 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
2328 2327214 : UnlockBufHdr(buf_hdr, buf_state);
2329 :
2330 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2331 :
2332 : /* finally delete buffer from the buffer mapping table */
2333 2327214 : BufTableDelete(&tag, hash);
2334 :
2335 2327214 : LWLockRelease(partition_lock);
2336 :
2337 : Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
2338 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2339 : Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
2340 :
2341 2327214 : return true;
2342 : }
2343 :
2344 : static Buffer
2345 3760420 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
2346 : {
2347 : BufferDesc *buf_hdr;
2348 : Buffer buf;
2349 : uint32 buf_state;
2350 : bool from_ring;
2351 :
2352 : /*
2353 : * Ensure, while the spinlock's not yet held, that there's a free refcount
2354 : * entry, and a resource owner slot for the pin.
2355 : */
2356 3760420 : ReservePrivateRefCountEntry();
2357 3760420 : ResourceOwnerEnlarge(CurrentResourceOwner);
2358 :
2359 : /* we return here if a prospective victim buffer gets used concurrently */
2360 12270 : again:
2361 :
2362 : /*
2363 : * Select a victim buffer. The buffer is returned with its header
2364 : * spinlock still held!
2365 : */
2366 3772690 : buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
2367 3772690 : buf = BufferDescriptorGetBuffer(buf_hdr);
2368 :
2369 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
2370 :
2371 : /* Pin the buffer and then release the buffer spinlock */
2372 3772690 : PinBuffer_Locked(buf_hdr);
2373 :
2374 : /*
2375 : * We shouldn't have any other pins for this buffer.
2376 : */
2377 3772690 : CheckBufferIsPinnedOnce(buf);
2378 :
2379 : /*
2380 : * If the buffer was dirty, try to write it out. There is a race
2381 : * condition here, in that someone might dirty it after we released the
2382 : * buffer header lock above, or even while we are writing it out (since
2383 : * our share-lock won't prevent hint-bit updates). We will recheck the
2384 : * dirty bit after re-locking the buffer header.
2385 : */
2386 3772690 : if (buf_state & BM_DIRTY)
2387 : {
2388 : LWLock *content_lock;
2389 :
2390 : Assert(buf_state & BM_TAG_VALID);
2391 : Assert(buf_state & BM_VALID);
2392 :
2393 : /*
2394 : * We need a share-lock on the buffer contents to write it out (else
2395 : * we might write invalid data, eg because someone else is compacting
2396 : * the page contents while we write). We must use a conditional lock
2397 : * acquisition here to avoid deadlock. Even though the buffer was not
2398 : * pinned (and therefore surely not locked) when StrategyGetBuffer
2399 : * returned it, someone else could have pinned and exclusive-locked it
2400 : * by the time we get here. If we try to get the lock unconditionally,
2401 : * we'd block waiting for them; if they later block waiting for us,
2402 : * deadlock ensues. (This has been observed to happen when two
2403 : * backends are both trying to split btree index pages, and the second
2404 : * one just happens to be trying to split the page the first one got
2405 : * from StrategyGetBuffer.)
2406 : */
2407 525130 : content_lock = BufferDescriptorGetContentLock(buf_hdr);
2408 525130 : if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
2409 : {
2410 : /*
2411 : * Someone else has locked the buffer, so give it up and loop back
2412 : * to get another one.
2413 : */
2414 0 : UnpinBuffer(buf_hdr);
2415 0 : goto again;
2416 : }
2417 :
2418 : /*
2419 : * If using a nondefault strategy, and writing the buffer would
2420 : * require a WAL flush, let the strategy decide whether to go ahead
2421 : * and write/reuse the buffer or to choose another victim. We need a
2422 : * lock to inspect the page LSN, so this can't be done inside
2423 : * StrategyGetBuffer.
2424 : */
2425 525130 : if (strategy != NULL)
2426 : {
2427 : XLogRecPtr lsn;
2428 :
2429 : /* Read the LSN while holding buffer header lock */
2430 147166 : buf_state = LockBufHdr(buf_hdr);
2431 147166 : lsn = BufferGetLSN(buf_hdr);
2432 147166 : UnlockBufHdr(buf_hdr, buf_state);
2433 :
2434 147166 : if (XLogNeedsFlush(lsn)
2435 17596 : && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
2436 : {
2437 11536 : LWLockRelease(content_lock);
2438 11536 : UnpinBuffer(buf_hdr);
2439 11536 : goto again;
2440 : }
2441 : }
2442 :
2443 : /* OK, do the I/O */
2444 513594 : FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
2445 513594 : LWLockRelease(content_lock);
2446 :
2447 513594 : ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
2448 : &buf_hdr->tag);
2449 : }
2450 :
2451 :
2452 3761154 : if (buf_state & BM_VALID)
2453 : {
2454 : /*
2455 : * When a BufferAccessStrategy is in use, blocks evicted from shared
2456 : * buffers are counted as IOOP_EVICT in the corresponding context
2457 : * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
2458 : * strategy in two cases: 1) while initially claiming buffers for the
2459 : * strategy ring 2) to replace an existing strategy ring buffer
2460 : * because it is pinned or in use and cannot be reused.
2461 : *
2462 : * Blocks evicted from buffers already in the strategy ring are
2463 : * counted as IOOP_REUSE in the corresponding strategy context.
2464 : *
2465 : * At this point, we can accurately count evictions and reuses,
2466 : * because we have successfully claimed the valid buffer. Previously,
2467 : * we may have been forced to release the buffer due to concurrent
2468 : * pinners or erroring out.
2469 : */
2470 2323678 : pgstat_count_io_op(IOOBJECT_RELATION, io_context,
2471 2323678 : from_ring ? IOOP_REUSE : IOOP_EVICT, 1, 0);
2472 : }
2473 :
2474 : /*
2475 : * If the buffer has an entry in the buffer mapping table, delete it. This
2476 : * can fail because another backend could have pinned or dirtied the
2477 : * buffer.
2478 : */
2479 3761154 : if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
2480 : {
2481 734 : UnpinBuffer(buf_hdr);
2482 734 : goto again;
2483 : }
2484 :
2485 : /* a final set of sanity checks */
2486 : #ifdef USE_ASSERT_CHECKING
2487 : buf_state = pg_atomic_read_u32(&buf_hdr->state);
2488 :
2489 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2490 : Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
2491 :
2492 : CheckBufferIsPinnedOnce(buf);
2493 : #endif
2494 :
2495 3760420 : return buf;
2496 : }
2497 :
2498 : /*
2499 : * Return the maximum number of buffers that a backend should try to pin once,
2500 : * to avoid exceeding its fair share. This is the highest value that
2501 : * GetAdditionalPinLimit() could ever return. Note that it may be zero on a
2502 : * system with a very small buffer pool relative to max_connections.
2503 : */
2504 : uint32
2505 1262344 : GetPinLimit(void)
2506 : {
2507 1262344 : return MaxProportionalPins;
2508 : }
2509 :
2510 : /*
2511 : * Return the maximum number of additional buffers that this backend should
2512 : * pin if it wants to stay under the per-backend limit, considering the number
2513 : * of buffers it has already pinned. Unlike LimitAdditionalPins(), the limit
2514 : * return by this function can be zero.
2515 : */
2516 : uint32
2517 7620558 : GetAdditionalPinLimit(void)
2518 : {
2519 : uint32 estimated_pins_held;
2520 :
2521 : /*
2522 : * We get the number of "overflowed" pins for free, but don't know the
2523 : * number of pins in PrivateRefCountArray. The cost of calculating that
2524 : * exactly doesn't seem worth it, so just assume the max.
2525 : */
2526 7620558 : estimated_pins_held = PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
2527 :
2528 : /* Is this backend already holding more than its fair share? */
2529 7620558 : if (estimated_pins_held > MaxProportionalPins)
2530 2355450 : return 0;
2531 :
2532 5265108 : return MaxProportionalPins - estimated_pins_held;
2533 : }
2534 :
2535 : /*
2536 : * Limit the number of pins a batch operation may additionally acquire, to
2537 : * avoid running out of pinnable buffers.
2538 : *
2539 : * One additional pin is always allowed, on the assumption that the operation
2540 : * requires at least one to make progress.
2541 : */
2542 : void
2543 401462 : LimitAdditionalPins(uint32 *additional_pins)
2544 : {
2545 : uint32 limit;
2546 :
2547 401462 : if (*additional_pins <= 1)
2548 381712 : return;
2549 :
2550 19750 : limit = GetAdditionalPinLimit();
2551 19750 : limit = Max(limit, 1);
2552 19750 : if (limit < *additional_pins)
2553 10942 : *additional_pins = limit;
2554 : }
2555 :
2556 : /*
2557 : * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
2558 : * avoid duplicating the tracing and relpersistence related logic.
2559 : */
2560 : static BlockNumber
2561 424236 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
2562 : ForkNumber fork,
2563 : BufferAccessStrategy strategy,
2564 : uint32 flags,
2565 : uint32 extend_by,
2566 : BlockNumber extend_upto,
2567 : Buffer *buffers,
2568 : uint32 *extended_by)
2569 : {
2570 : BlockNumber first_block;
2571 :
2572 : TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
2573 : bmr.smgr->smgr_rlocator.locator.spcOid,
2574 : bmr.smgr->smgr_rlocator.locator.dbOid,
2575 : bmr.smgr->smgr_rlocator.locator.relNumber,
2576 : bmr.smgr->smgr_rlocator.backend,
2577 : extend_by);
2578 :
2579 424236 : if (bmr.relpersistence == RELPERSISTENCE_TEMP)
2580 22774 : first_block = ExtendBufferedRelLocal(bmr, fork, flags,
2581 : extend_by, extend_upto,
2582 : buffers, &extend_by);
2583 : else
2584 401462 : first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
2585 : extend_by, extend_upto,
2586 : buffers, &extend_by);
2587 424236 : *extended_by = extend_by;
2588 :
2589 : TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
2590 : bmr.smgr->smgr_rlocator.locator.spcOid,
2591 : bmr.smgr->smgr_rlocator.locator.dbOid,
2592 : bmr.smgr->smgr_rlocator.locator.relNumber,
2593 : bmr.smgr->smgr_rlocator.backend,
2594 : *extended_by,
2595 : first_block);
2596 :
2597 424236 : return first_block;
2598 : }
2599 :
2600 : /*
2601 : * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
2602 : * shared buffers.
2603 : */
2604 : static BlockNumber
2605 401462 : ExtendBufferedRelShared(BufferManagerRelation bmr,
2606 : ForkNumber fork,
2607 : BufferAccessStrategy strategy,
2608 : uint32 flags,
2609 : uint32 extend_by,
2610 : BlockNumber extend_upto,
2611 : Buffer *buffers,
2612 : uint32 *extended_by)
2613 : {
2614 : BlockNumber first_block;
2615 401462 : IOContext io_context = IOContextForStrategy(strategy);
2616 : instr_time io_start;
2617 :
2618 401462 : LimitAdditionalPins(&extend_by);
2619 :
2620 : /*
2621 : * Acquire victim buffers for extension without holding extension lock.
2622 : * Writing out victim buffers is the most expensive part of extending the
2623 : * relation, particularly when doing so requires WAL flushes. Zeroing out
2624 : * the buffers is also quite expensive, so do that before holding the
2625 : * extension lock as well.
2626 : *
2627 : * These pages are pinned by us and not valid. While we hold the pin they
2628 : * can't be acquired as victim buffers by another backend.
2629 : */
2630 845128 : for (uint32 i = 0; i < extend_by; i++)
2631 : {
2632 : Block buf_block;
2633 :
2634 443666 : buffers[i] = GetVictimBuffer(strategy, io_context);
2635 443666 : buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
2636 :
2637 : /* new buffers are zero-filled */
2638 443666 : MemSet(buf_block, 0, BLCKSZ);
2639 : }
2640 :
2641 : /*
2642 : * Lock relation against concurrent extensions, unless requested not to.
2643 : *
2644 : * We use the same extension lock for all forks. That's unnecessarily
2645 : * restrictive, but currently extensions for forks don't happen often
2646 : * enough to make it worth locking more granularly.
2647 : *
2648 : * Note that another backend might have extended the relation by the time
2649 : * we get the lock.
2650 : */
2651 401462 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2652 298508 : LockRelationForExtension(bmr.rel, ExclusiveLock);
2653 :
2654 : /*
2655 : * If requested, invalidate size cache, so that smgrnblocks asks the
2656 : * kernel.
2657 : */
2658 401462 : if (flags & EB_CLEAR_SIZE_CACHE)
2659 15286 : bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
2660 :
2661 401462 : first_block = smgrnblocks(bmr.smgr, fork);
2662 :
2663 : /*
2664 : * Now that we have the accurate relation size, check if the caller wants
2665 : * us to extend to only up to a specific size. If there were concurrent
2666 : * extensions, we might have acquired too many buffers and need to release
2667 : * them.
2668 : */
2669 401462 : if (extend_upto != InvalidBlockNumber)
2670 : {
2671 106444 : uint32 orig_extend_by = extend_by;
2672 :
2673 106444 : if (first_block > extend_upto)
2674 0 : extend_by = 0;
2675 106444 : else if ((uint64) first_block + extend_by > extend_upto)
2676 4 : extend_by = extend_upto - first_block;
2677 :
2678 106456 : for (uint32 i = extend_by; i < orig_extend_by; i++)
2679 : {
2680 12 : BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
2681 :
2682 : /*
2683 : * The victim buffer we acquired previously is clean and unused,
2684 : * let it be found again quickly
2685 : */
2686 12 : StrategyFreeBuffer(buf_hdr);
2687 12 : UnpinBuffer(buf_hdr);
2688 : }
2689 :
2690 106444 : if (extend_by == 0)
2691 : {
2692 4 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2693 4 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2694 4 : *extended_by = extend_by;
2695 4 : return first_block;
2696 : }
2697 : }
2698 :
2699 : /* Fail if relation is already at maximum possible length */
2700 401458 : if ((uint64) first_block + extend_by >= MaxBlockNumber)
2701 0 : ereport(ERROR,
2702 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
2703 : errmsg("cannot extend relation %s beyond %u blocks",
2704 : relpath(bmr.smgr->smgr_rlocator, fork).str,
2705 : MaxBlockNumber)));
2706 :
2707 : /*
2708 : * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
2709 : *
2710 : * This needs to happen before we extend the relation, because as soon as
2711 : * we do, other backends can start to read in those pages.
2712 : */
2713 845112 : for (uint32 i = 0; i < extend_by; i++)
2714 : {
2715 443654 : Buffer victim_buf = buffers[i];
2716 443654 : BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
2717 : BufferTag tag;
2718 : uint32 hash;
2719 : LWLock *partition_lock;
2720 : int existing_id;
2721 :
2722 : /* in case we need to pin an existing buffer below */
2723 443654 : ResourceOwnerEnlarge(CurrentResourceOwner);
2724 443654 : ReservePrivateRefCountEntry();
2725 :
2726 443654 : InitBufferTag(&tag, &bmr.smgr->smgr_rlocator.locator, fork, first_block + i);
2727 443654 : hash = BufTableHashCode(&tag);
2728 443654 : partition_lock = BufMappingPartitionLock(hash);
2729 :
2730 443654 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
2731 :
2732 443654 : existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
2733 :
2734 : /*
2735 : * We get here only in the corner case where we are trying to extend
2736 : * the relation but we found a pre-existing buffer. This can happen
2737 : * because a prior attempt at extending the relation failed, and
2738 : * because mdread doesn't complain about reads beyond EOF (when
2739 : * zero_damaged_pages is ON) and so a previous attempt to read a block
2740 : * beyond EOF could have left a "valid" zero-filled buffer.
2741 : *
2742 : * This has also been observed when relation was overwritten by
2743 : * external process. Since the legitimate cases should always have
2744 : * left a zero-filled buffer, complain if not PageIsNew.
2745 : */
2746 443654 : if (existing_id >= 0)
2747 : {
2748 0 : BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
2749 : Block buf_block;
2750 : bool valid;
2751 :
2752 : /*
2753 : * Pin the existing buffer before releasing the partition lock,
2754 : * preventing it from being evicted.
2755 : */
2756 0 : valid = PinBuffer(existing_hdr, strategy);
2757 :
2758 0 : LWLockRelease(partition_lock);
2759 :
2760 : /*
2761 : * The victim buffer we acquired previously is clean and unused,
2762 : * let it be found again quickly
2763 : */
2764 0 : StrategyFreeBuffer(victim_buf_hdr);
2765 0 : UnpinBuffer(victim_buf_hdr);
2766 :
2767 0 : buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
2768 0 : buf_block = BufHdrGetBlock(existing_hdr);
2769 :
2770 0 : if (valid && !PageIsNew((Page) buf_block))
2771 0 : ereport(ERROR,
2772 : (errmsg("unexpected data beyond EOF in block %u of relation %s",
2773 : existing_hdr->tag.blockNum,
2774 : relpath(bmr.smgr->smgr_rlocator, fork).str)));
2775 :
2776 : /*
2777 : * We *must* do smgr[zero]extend before succeeding, else the page
2778 : * will not be reserved by the kernel, and the next P_NEW call
2779 : * will decide to return the same page. Clear the BM_VALID bit,
2780 : * do StartBufferIO() and proceed.
2781 : *
2782 : * Loop to handle the very small possibility that someone re-sets
2783 : * BM_VALID between our clearing it and StartBufferIO inspecting
2784 : * it.
2785 : */
2786 : do
2787 : {
2788 0 : uint32 buf_state = LockBufHdr(existing_hdr);
2789 :
2790 0 : buf_state &= ~BM_VALID;
2791 0 : UnlockBufHdr(existing_hdr, buf_state);
2792 0 : } while (!StartBufferIO(existing_hdr, true, false));
2793 : }
2794 : else
2795 : {
2796 : uint32 buf_state;
2797 :
2798 443654 : buf_state = LockBufHdr(victim_buf_hdr);
2799 :
2800 : /* some sanity checks while we hold the buffer header lock */
2801 : Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
2802 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2803 :
2804 443654 : victim_buf_hdr->tag = tag;
2805 :
2806 443654 : buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2807 443654 : if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
2808 433098 : buf_state |= BM_PERMANENT;
2809 :
2810 443654 : UnlockBufHdr(victim_buf_hdr, buf_state);
2811 :
2812 443654 : LWLockRelease(partition_lock);
2813 :
2814 : /* XXX: could combine the locked operations in it with the above */
2815 443654 : StartBufferIO(victim_buf_hdr, true, false);
2816 : }
2817 : }
2818 :
2819 401458 : io_start = pgstat_prepare_io_time(track_io_timing);
2820 :
2821 : /*
2822 : * Note: if smgrzeroextend fails, we will end up with buffers that are
2823 : * allocated but not marked BM_VALID. The next relation extension will
2824 : * still select the same block number (because the relation didn't get any
2825 : * longer on disk) and so future attempts to extend the relation will find
2826 : * the same buffers (if they have not been recycled) but come right back
2827 : * here to try smgrzeroextend again.
2828 : *
2829 : * We don't need to set checksum for all-zero pages.
2830 : */
2831 401458 : smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
2832 :
2833 : /*
2834 : * Release the file-extension lock; it's now OK for someone else to extend
2835 : * the relation some more.
2836 : *
2837 : * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
2838 : * take noticeable time.
2839 : */
2840 401458 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2841 298504 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2842 :
2843 401458 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
2844 401458 : io_start, 1, extend_by * BLCKSZ);
2845 :
2846 : /* Set BM_VALID, terminate IO, and wake up any waiters */
2847 845112 : for (uint32 i = 0; i < extend_by; i++)
2848 : {
2849 443654 : Buffer buf = buffers[i];
2850 443654 : BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
2851 443654 : bool lock = false;
2852 :
2853 443654 : if (flags & EB_LOCK_FIRST && i == 0)
2854 294486 : lock = true;
2855 149168 : else if (flags & EB_LOCK_TARGET)
2856 : {
2857 : Assert(extend_upto != InvalidBlockNumber);
2858 89060 : if (first_block + i + 1 == extend_upto)
2859 87882 : lock = true;
2860 : }
2861 :
2862 443654 : if (lock)
2863 382368 : LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
2864 :
2865 443654 : TerminateBufferIO(buf_hdr, false, BM_VALID, true, false);
2866 : }
2867 :
2868 401458 : pgBufferUsage.shared_blks_written += extend_by;
2869 :
2870 401458 : *extended_by = extend_by;
2871 :
2872 401458 : return first_block;
2873 : }
2874 :
2875 : /*
2876 : * BufferIsExclusiveLocked
2877 : *
2878 : * Checks if buffer is exclusive-locked.
2879 : *
2880 : * Buffer must be pinned.
2881 : */
2882 : bool
2883 0 : BufferIsExclusiveLocked(Buffer buffer)
2884 : {
2885 : BufferDesc *bufHdr;
2886 :
2887 : Assert(BufferIsPinned(buffer));
2888 :
2889 0 : if (BufferIsLocal(buffer))
2890 : {
2891 : /* Content locks are not maintained for local buffers. */
2892 0 : return true;
2893 : }
2894 : else
2895 : {
2896 0 : bufHdr = GetBufferDescriptor(buffer - 1);
2897 0 : return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2898 : LW_EXCLUSIVE);
2899 : }
2900 : }
2901 :
2902 : /*
2903 : * BufferIsDirty
2904 : *
2905 : * Checks if buffer is already dirty.
2906 : *
2907 : * Buffer must be pinned and exclusive-locked. (Without an exclusive lock,
2908 : * the result may be stale before it's returned.)
2909 : */
2910 : bool
2911 0 : BufferIsDirty(Buffer buffer)
2912 : {
2913 : BufferDesc *bufHdr;
2914 :
2915 : Assert(BufferIsPinned(buffer));
2916 :
2917 0 : if (BufferIsLocal(buffer))
2918 : {
2919 0 : int bufid = -buffer - 1;
2920 :
2921 0 : bufHdr = GetLocalBufferDescriptor(bufid);
2922 : /* Content locks are not maintained for local buffers. */
2923 : }
2924 : else
2925 : {
2926 0 : bufHdr = GetBufferDescriptor(buffer - 1);
2927 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2928 : LW_EXCLUSIVE));
2929 : }
2930 :
2931 0 : return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
2932 : }
2933 :
2934 : /*
2935 : * MarkBufferDirty
2936 : *
2937 : * Marks buffer contents as dirty (actual write happens later).
2938 : *
2939 : * Buffer must be pinned and exclusive-locked. (If caller does not hold
2940 : * exclusive lock, then somebody could be in process of writing the buffer,
2941 : * leading to risk of bad data written to disk.)
2942 : */
2943 : void
2944 42826106 : MarkBufferDirty(Buffer buffer)
2945 : {
2946 : BufferDesc *bufHdr;
2947 : uint32 buf_state;
2948 : uint32 old_buf_state;
2949 :
2950 42826106 : if (!BufferIsValid(buffer))
2951 0 : elog(ERROR, "bad buffer ID: %d", buffer);
2952 :
2953 42826106 : if (BufferIsLocal(buffer))
2954 : {
2955 2444336 : MarkLocalBufferDirty(buffer);
2956 2444336 : return;
2957 : }
2958 :
2959 40381770 : bufHdr = GetBufferDescriptor(buffer - 1);
2960 :
2961 : Assert(BufferIsPinned(buffer));
2962 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2963 : LW_EXCLUSIVE));
2964 :
2965 40381770 : old_buf_state = pg_atomic_read_u32(&bufHdr->state);
2966 : for (;;)
2967 : {
2968 40381998 : if (old_buf_state & BM_LOCKED)
2969 32 : old_buf_state = WaitBufHdrUnlocked(bufHdr);
2970 :
2971 40381998 : buf_state = old_buf_state;
2972 :
2973 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2974 40381998 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
2975 :
2976 40381998 : if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
2977 : buf_state))
2978 40381770 : break;
2979 : }
2980 :
2981 : /*
2982 : * If the buffer was not dirty already, do vacuum accounting.
2983 : */
2984 40381770 : if (!(old_buf_state & BM_DIRTY))
2985 : {
2986 1277096 : pgBufferUsage.shared_blks_dirtied++;
2987 1277096 : if (VacuumCostActive)
2988 14434 : VacuumCostBalance += VacuumCostPageDirty;
2989 : }
2990 : }
2991 :
2992 : /*
2993 : * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
2994 : *
2995 : * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
2996 : * compared to calling the two routines separately. Now it's mainly just
2997 : * a convenience function. However, if the passed buffer is valid and
2998 : * already contains the desired block, we just return it as-is; and that
2999 : * does save considerable work compared to a full release and reacquire.
3000 : *
3001 : * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
3002 : * buffer actually needs to be released. This case is the same as ReadBuffer,
3003 : * but can save some tests in the caller.
3004 : */
3005 : Buffer
3006 56642574 : ReleaseAndReadBuffer(Buffer buffer,
3007 : Relation relation,
3008 : BlockNumber blockNum)
3009 : {
3010 56642574 : ForkNumber forkNum = MAIN_FORKNUM;
3011 : BufferDesc *bufHdr;
3012 :
3013 56642574 : if (BufferIsValid(buffer))
3014 : {
3015 : Assert(BufferIsPinned(buffer));
3016 33816226 : if (BufferIsLocal(buffer))
3017 : {
3018 73728 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3019 80772 : if (bufHdr->tag.blockNum == blockNum &&
3020 14088 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
3021 7044 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
3022 7044 : return buffer;
3023 66684 : UnpinLocalBuffer(buffer);
3024 : }
3025 : else
3026 : {
3027 33742498 : bufHdr = GetBufferDescriptor(buffer - 1);
3028 : /* we have pin, so it's ok to examine tag without spinlock */
3029 45287322 : if (bufHdr->tag.blockNum == blockNum &&
3030 23089648 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
3031 11544824 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
3032 11544824 : return buffer;
3033 22197674 : UnpinBuffer(bufHdr);
3034 : }
3035 : }
3036 :
3037 45090706 : return ReadBuffer(relation, blockNum);
3038 : }
3039 :
3040 : /*
3041 : * PinBuffer -- make buffer unavailable for replacement.
3042 : *
3043 : * For the default access strategy, the buffer's usage_count is incremented
3044 : * when we first pin it; for other strategies we just make sure the usage_count
3045 : * isn't zero. (The idea of the latter is that we don't want synchronized
3046 : * heap scans to inflate the count, but we need it to not be zero to discourage
3047 : * other backends from stealing buffers from our ring. As long as we cycle
3048 : * through the ring faster than the global clock-sweep cycles, buffers in
3049 : * our ring won't be chosen as victims for replacement by other backends.)
3050 : *
3051 : * This should be applied only to shared buffers, never local ones.
3052 : *
3053 : * Since buffers are pinned/unpinned very frequently, pin buffers without
3054 : * taking the buffer header lock; instead update the state variable in loop of
3055 : * CAS operations. Hopefully it's just a single CAS.
3056 : *
3057 : * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
3058 : * must have been done already.
3059 : *
3060 : * Returns true if buffer is BM_VALID, else false. This provision allows
3061 : * some callers to avoid an extra spinlock cycle.
3062 : */
3063 : static bool
3064 116391158 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
3065 : {
3066 116391158 : Buffer b = BufferDescriptorGetBuffer(buf);
3067 : bool result;
3068 : PrivateRefCountEntry *ref;
3069 :
3070 : Assert(!BufferIsLocal(b));
3071 : Assert(ReservedRefCountEntry != NULL);
3072 :
3073 116391158 : ref = GetPrivateRefCountEntry(b, true);
3074 :
3075 116391158 : if (ref == NULL)
3076 : {
3077 : uint32 buf_state;
3078 : uint32 old_buf_state;
3079 :
3080 112098816 : ref = NewPrivateRefCountEntry(b);
3081 :
3082 112098816 : old_buf_state = pg_atomic_read_u32(&buf->state);
3083 : for (;;)
3084 : {
3085 112144062 : if (old_buf_state & BM_LOCKED)
3086 1734 : old_buf_state = WaitBufHdrUnlocked(buf);
3087 :
3088 112144062 : buf_state = old_buf_state;
3089 :
3090 : /* increase refcount */
3091 112144062 : buf_state += BUF_REFCOUNT_ONE;
3092 :
3093 112144062 : if (strategy == NULL)
3094 : {
3095 : /* Default case: increase usagecount unless already max. */
3096 110698194 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
3097 6436500 : buf_state += BUF_USAGECOUNT_ONE;
3098 : }
3099 : else
3100 : {
3101 : /*
3102 : * Ring buffers shouldn't evict others from pool. Thus we
3103 : * don't make usagecount more than 1.
3104 : */
3105 1445868 : if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
3106 68310 : buf_state += BUF_USAGECOUNT_ONE;
3107 : }
3108 :
3109 112144062 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
3110 : buf_state))
3111 : {
3112 112098816 : result = (buf_state & BM_VALID) != 0;
3113 :
3114 : /*
3115 : * Assume that we acquired a buffer pin for the purposes of
3116 : * Valgrind buffer client checks (even in !result case) to
3117 : * keep things simple. Buffers that are unsafe to access are
3118 : * not generally guaranteed to be marked undefined or
3119 : * non-accessible in any case.
3120 : */
3121 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
3122 112098816 : break;
3123 : }
3124 : }
3125 : }
3126 : else
3127 : {
3128 : /*
3129 : * If we previously pinned the buffer, it is likely to be valid, but
3130 : * it may not be if StartReadBuffers() was called and
3131 : * WaitReadBuffers() hasn't been called yet. We'll check by loading
3132 : * the flags without locking. This is racy, but it's OK to return
3133 : * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
3134 : * it'll see that it's now valid.
3135 : *
3136 : * Note: We deliberately avoid a Valgrind client request here.
3137 : * Individual access methods can optionally superimpose buffer page
3138 : * client requests on top of our client requests to enforce that
3139 : * buffers are only accessed while locked (and pinned). It's possible
3140 : * that the buffer page is legitimately non-accessible here. We
3141 : * cannot meddle with that.
3142 : */
3143 4292342 : result = (pg_atomic_read_u32(&buf->state) & BM_VALID) != 0;
3144 : }
3145 :
3146 116391158 : ref->refcount++;
3147 : Assert(ref->refcount > 0);
3148 116391158 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
3149 116391158 : return result;
3150 : }
3151 :
3152 : /*
3153 : * PinBuffer_Locked -- as above, but caller already locked the buffer header.
3154 : * The spinlock is released before return.
3155 : *
3156 : * As this function is called with the spinlock held, the caller has to
3157 : * previously call ReservePrivateRefCountEntry() and
3158 : * ResourceOwnerEnlarge(CurrentResourceOwner);
3159 : *
3160 : * Currently, no callers of this function want to modify the buffer's
3161 : * usage_count at all, so there's no need for a strategy parameter.
3162 : * Also we don't bother with a BM_VALID test (the caller could check that for
3163 : * itself).
3164 : *
3165 : * Also all callers only ever use this function when it's known that the
3166 : * buffer can't have a preexisting pin by this backend. That allows us to skip
3167 : * searching the private refcount array & hash, which is a boon, because the
3168 : * spinlock is still held.
3169 : *
3170 : * Note: use of this routine is frequently mandatory, not just an optimization
3171 : * to save a spin lock/unlock cycle, because we need to pin a buffer before
3172 : * its state can change under us.
3173 : */
3174 : static void
3175 4369012 : PinBuffer_Locked(BufferDesc *buf)
3176 : {
3177 : Buffer b;
3178 : PrivateRefCountEntry *ref;
3179 : uint32 buf_state;
3180 :
3181 : /*
3182 : * As explained, We don't expect any preexisting pins. That allows us to
3183 : * manipulate the PrivateRefCount after releasing the spinlock
3184 : */
3185 : Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
3186 :
3187 : /*
3188 : * Buffer can't have a preexisting pin, so mark its page as defined to
3189 : * Valgrind (this is similar to the PinBuffer() case where the backend
3190 : * doesn't already have a buffer pin)
3191 : */
3192 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
3193 :
3194 : /*
3195 : * Since we hold the buffer spinlock, we can update the buffer state and
3196 : * release the lock in one operation.
3197 : */
3198 4369012 : buf_state = pg_atomic_read_u32(&buf->state);
3199 : Assert(buf_state & BM_LOCKED);
3200 4369012 : buf_state += BUF_REFCOUNT_ONE;
3201 4369012 : UnlockBufHdr(buf, buf_state);
3202 :
3203 4369012 : b = BufferDescriptorGetBuffer(buf);
3204 :
3205 4369012 : ref = NewPrivateRefCountEntry(b);
3206 4369012 : ref->refcount++;
3207 :
3208 4369012 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
3209 4369012 : }
3210 :
3211 : /*
3212 : * Support for waking up another backend that is waiting for the cleanup lock
3213 : * to be released using BM_PIN_COUNT_WAITER.
3214 : *
3215 : * See LockBufferForCleanup().
3216 : *
3217 : * Expected to be called just after releasing a buffer pin (in a BufferDesc,
3218 : * not just reducing the backend-local pincount for the buffer).
3219 : */
3220 : static void
3221 140 : WakePinCountWaiter(BufferDesc *buf)
3222 : {
3223 : /*
3224 : * Acquire the buffer header lock, re-check that there's a waiter. Another
3225 : * backend could have unpinned this buffer, and already woken up the
3226 : * waiter.
3227 : *
3228 : * There's no danger of the buffer being replaced after we unpinned it
3229 : * above, as it's pinned by the waiter. The waiter removes
3230 : * BM_PIN_COUNT_WAITER if it stops waiting for a reason other than this
3231 : * backend waking it up.
3232 : */
3233 140 : uint32 buf_state = LockBufHdr(buf);
3234 :
3235 140 : if ((buf_state & BM_PIN_COUNT_WAITER) &&
3236 140 : BUF_STATE_GET_REFCOUNT(buf_state) == 1)
3237 140 : {
3238 : /* we just released the last pin other than the waiter's */
3239 140 : int wait_backend_pgprocno = buf->wait_backend_pgprocno;
3240 :
3241 140 : buf_state &= ~BM_PIN_COUNT_WAITER;
3242 140 : UnlockBufHdr(buf, buf_state);
3243 140 : ProcSendSignal(wait_backend_pgprocno);
3244 : }
3245 : else
3246 0 : UnlockBufHdr(buf, buf_state);
3247 140 : }
3248 :
3249 : /*
3250 : * UnpinBuffer -- make buffer available for replacement.
3251 : *
3252 : * This should be applied only to shared buffers, never local ones. This
3253 : * always adjusts CurrentResourceOwner.
3254 : */
3255 : static void
3256 142873050 : UnpinBuffer(BufferDesc *buf)
3257 : {
3258 142873050 : Buffer b = BufferDescriptorGetBuffer(buf);
3259 :
3260 142873050 : ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
3261 142873050 : UnpinBufferNoOwner(buf);
3262 142873050 : }
3263 :
3264 : static void
3265 142881862 : UnpinBufferNoOwner(BufferDesc *buf)
3266 : {
3267 : PrivateRefCountEntry *ref;
3268 142881862 : Buffer b = BufferDescriptorGetBuffer(buf);
3269 :
3270 : Assert(!BufferIsLocal(b));
3271 :
3272 : /* not moving as we're likely deleting it soon anyway */
3273 142881862 : ref = GetPrivateRefCountEntry(b, false);
3274 : Assert(ref != NULL);
3275 : Assert(ref->refcount > 0);
3276 142881862 : ref->refcount--;
3277 142881862 : if (ref->refcount == 0)
3278 : {
3279 : uint32 buf_state;
3280 : uint32 old_buf_state;
3281 :
3282 : /*
3283 : * Mark buffer non-accessible to Valgrind.
3284 : *
3285 : * Note that the buffer may have already been marked non-accessible
3286 : * within access method code that enforces that buffers are only
3287 : * accessed while a buffer lock is held.
3288 : */
3289 : VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
3290 :
3291 : /* I'd better not still hold the buffer content lock */
3292 : Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
3293 :
3294 : /*
3295 : * Decrement the shared reference count.
3296 : *
3297 : * Since buffer spinlock holder can update status using just write,
3298 : * it's not safe to use atomic decrement here; thus use a CAS loop.
3299 : */
3300 116467828 : old_buf_state = pg_atomic_read_u32(&buf->state);
3301 : for (;;)
3302 : {
3303 116508830 : if (old_buf_state & BM_LOCKED)
3304 1860 : old_buf_state = WaitBufHdrUnlocked(buf);
3305 :
3306 116508830 : buf_state = old_buf_state;
3307 :
3308 116508830 : buf_state -= BUF_REFCOUNT_ONE;
3309 :
3310 116508830 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
3311 : buf_state))
3312 116467828 : break;
3313 : }
3314 :
3315 : /* Support LockBufferForCleanup() */
3316 116467828 : if (buf_state & BM_PIN_COUNT_WAITER)
3317 140 : WakePinCountWaiter(buf);
3318 :
3319 116467828 : ForgetPrivateRefCountEntry(ref);
3320 : }
3321 142881862 : }
3322 :
3323 : #define ST_SORT sort_checkpoint_bufferids
3324 : #define ST_ELEMENT_TYPE CkptSortItem
3325 : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
3326 : #define ST_SCOPE static
3327 : #define ST_DEFINE
3328 : #include "lib/sort_template.h"
3329 :
3330 : /*
3331 : * BufferSync -- Write out all dirty buffers in the pool.
3332 : *
3333 : * This is called at checkpoint time to write out all dirty shared buffers.
3334 : * The checkpoint request flags should be passed in. If CHECKPOINT_FAST is
3335 : * set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
3336 : * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_UNLOGGED is set, we write
3337 : * even unlogged buffers, which are otherwise skipped. The remaining flags
3338 : * currently have no effect here.
3339 : */
3340 : static void
3341 3362 : BufferSync(int flags)
3342 : {
3343 : uint32 buf_state;
3344 : int buf_id;
3345 : int num_to_scan;
3346 : int num_spaces;
3347 : int num_processed;
3348 : int num_written;
3349 3362 : CkptTsStatus *per_ts_stat = NULL;
3350 : Oid last_tsid;
3351 : binaryheap *ts_heap;
3352 : int i;
3353 3362 : int mask = BM_DIRTY;
3354 : WritebackContext wb_context;
3355 :
3356 : /*
3357 : * Unless this is a shutdown checkpoint or we have been explicitly told,
3358 : * we write only permanent, dirty buffers. But at shutdown or end of
3359 : * recovery, we write all dirty buffers.
3360 : */
3361 3362 : if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
3362 : CHECKPOINT_FLUSH_UNLOGGED))))
3363 1912 : mask |= BM_PERMANENT;
3364 :
3365 : /*
3366 : * Loop over all buffers, and mark the ones that need to be written with
3367 : * BM_CHECKPOINT_NEEDED. Count them as we go (num_to_scan), so that we
3368 : * can estimate how much work needs to be done.
3369 : *
3370 : * This allows us to write only those pages that were dirty when the
3371 : * checkpoint began, and not those that get dirtied while it proceeds.
3372 : * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
3373 : * later in this function, or by normal backends or the bgwriter cleaning
3374 : * scan, the flag is cleared. Any buffer dirtied after this point won't
3375 : * have the flag set.
3376 : *
3377 : * Note that if we fail to write some buffer, we may leave buffers with
3378 : * BM_CHECKPOINT_NEEDED still set. This is OK since any such buffer would
3379 : * certainly need to be written for the next checkpoint attempt, too.
3380 : */
3381 3362 : num_to_scan = 0;
3382 23386562 : for (buf_id = 0; buf_id < NBuffers; buf_id++)
3383 : {
3384 23383200 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
3385 :
3386 : /*
3387 : * Header spinlock is enough to examine BM_DIRTY, see comment in
3388 : * SyncOneBuffer.
3389 : */
3390 23383200 : buf_state = LockBufHdr(bufHdr);
3391 :
3392 23383200 : if ((buf_state & mask) == mask)
3393 : {
3394 : CkptSortItem *item;
3395 :
3396 578142 : buf_state |= BM_CHECKPOINT_NEEDED;
3397 :
3398 578142 : item = &CkptBufferIds[num_to_scan++];
3399 578142 : item->buf_id = buf_id;
3400 578142 : item->tsId = bufHdr->tag.spcOid;
3401 578142 : item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
3402 578142 : item->forkNum = BufTagGetForkNum(&bufHdr->tag);
3403 578142 : item->blockNum = bufHdr->tag.blockNum;
3404 : }
3405 :
3406 23383200 : UnlockBufHdr(bufHdr, buf_state);
3407 :
3408 : /* Check for barrier events in case NBuffers is large. */
3409 23383200 : if (ProcSignalBarrierPending)
3410 0 : ProcessProcSignalBarrier();
3411 : }
3412 :
3413 3362 : if (num_to_scan == 0)
3414 1286 : return; /* nothing to do */
3415 :
3416 2076 : WritebackContextInit(&wb_context, &checkpoint_flush_after);
3417 :
3418 : TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
3419 :
3420 : /*
3421 : * Sort buffers that need to be written to reduce the likelihood of random
3422 : * IO. The sorting is also important for the implementation of balancing
3423 : * writes between tablespaces. Without balancing writes we'd potentially
3424 : * end up writing to the tablespaces one-by-one; possibly overloading the
3425 : * underlying system.
3426 : */
3427 2076 : sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
3428 :
3429 2076 : num_spaces = 0;
3430 :
3431 : /*
3432 : * Allocate progress status for each tablespace with buffers that need to
3433 : * be flushed. This requires the to-be-flushed array to be sorted.
3434 : */
3435 2076 : last_tsid = InvalidOid;
3436 580218 : for (i = 0; i < num_to_scan; i++)
3437 : {
3438 : CkptTsStatus *s;
3439 : Oid cur_tsid;
3440 :
3441 578142 : cur_tsid = CkptBufferIds[i].tsId;
3442 :
3443 : /*
3444 : * Grow array of per-tablespace status structs, every time a new
3445 : * tablespace is found.
3446 : */
3447 578142 : if (last_tsid == InvalidOid || last_tsid != cur_tsid)
3448 3104 : {
3449 : Size sz;
3450 :
3451 3104 : num_spaces++;
3452 :
3453 : /*
3454 : * Not worth adding grow-by-power-of-2 logic here - even with a
3455 : * few hundred tablespaces this should be fine.
3456 : */
3457 3104 : sz = sizeof(CkptTsStatus) * num_spaces;
3458 :
3459 3104 : if (per_ts_stat == NULL)
3460 2076 : per_ts_stat = (CkptTsStatus *) palloc(sz);
3461 : else
3462 1028 : per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
3463 :
3464 3104 : s = &per_ts_stat[num_spaces - 1];
3465 3104 : memset(s, 0, sizeof(*s));
3466 3104 : s->tsId = cur_tsid;
3467 :
3468 : /*
3469 : * The first buffer in this tablespace. As CkptBufferIds is sorted
3470 : * by tablespace all (s->num_to_scan) buffers in this tablespace
3471 : * will follow afterwards.
3472 : */
3473 3104 : s->index = i;
3474 :
3475 : /*
3476 : * progress_slice will be determined once we know how many buffers
3477 : * are in each tablespace, i.e. after this loop.
3478 : */
3479 :
3480 3104 : last_tsid = cur_tsid;
3481 : }
3482 : else
3483 : {
3484 575038 : s = &per_ts_stat[num_spaces - 1];
3485 : }
3486 :
3487 578142 : s->num_to_scan++;
3488 :
3489 : /* Check for barrier events. */
3490 578142 : if (ProcSignalBarrierPending)
3491 0 : ProcessProcSignalBarrier();
3492 : }
3493 :
3494 : Assert(num_spaces > 0);
3495 :
3496 : /*
3497 : * Build a min-heap over the write-progress in the individual tablespaces,
3498 : * and compute how large a portion of the total progress a single
3499 : * processed buffer is.
3500 : */
3501 2076 : ts_heap = binaryheap_allocate(num_spaces,
3502 : ts_ckpt_progress_comparator,
3503 : NULL);
3504 :
3505 5180 : for (i = 0; i < num_spaces; i++)
3506 : {
3507 3104 : CkptTsStatus *ts_stat = &per_ts_stat[i];
3508 :
3509 3104 : ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
3510 :
3511 3104 : binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
3512 : }
3513 :
3514 2076 : binaryheap_build(ts_heap);
3515 :
3516 : /*
3517 : * Iterate through to-be-checkpointed buffers and write the ones (still)
3518 : * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
3519 : * tablespaces; otherwise the sorting would lead to only one tablespace
3520 : * receiving writes at a time, making inefficient use of the hardware.
3521 : */
3522 2076 : num_processed = 0;
3523 2076 : num_written = 0;
3524 580218 : while (!binaryheap_empty(ts_heap))
3525 : {
3526 578142 : BufferDesc *bufHdr = NULL;
3527 : CkptTsStatus *ts_stat = (CkptTsStatus *)
3528 578142 : DatumGetPointer(binaryheap_first(ts_heap));
3529 :
3530 578142 : buf_id = CkptBufferIds[ts_stat->index].buf_id;
3531 : Assert(buf_id != -1);
3532 :
3533 578142 : bufHdr = GetBufferDescriptor(buf_id);
3534 :
3535 578142 : num_processed++;
3536 :
3537 : /*
3538 : * We don't need to acquire the lock here, because we're only looking
3539 : * at a single bit. It's possible that someone else writes the buffer
3540 : * and clears the flag right after we check, but that doesn't matter
3541 : * since SyncOneBuffer will then do nothing. However, there is a
3542 : * further race condition: it's conceivable that between the time we
3543 : * examine the bit here and the time SyncOneBuffer acquires the lock,
3544 : * someone else not only wrote the buffer but replaced it with another
3545 : * page and dirtied it. In that improbable case, SyncOneBuffer will
3546 : * write the buffer though we didn't need to. It doesn't seem worth
3547 : * guarding against this, though.
3548 : */
3549 578142 : if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
3550 : {
3551 540504 : if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
3552 : {
3553 : TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
3554 540504 : PendingCheckpointerStats.buffers_written++;
3555 540504 : num_written++;
3556 : }
3557 : }
3558 :
3559 : /*
3560 : * Measure progress independent of actually having to flush the buffer
3561 : * - otherwise writing become unbalanced.
3562 : */
3563 578142 : ts_stat->progress += ts_stat->progress_slice;
3564 578142 : ts_stat->num_scanned++;
3565 578142 : ts_stat->index++;
3566 :
3567 : /* Have all the buffers from the tablespace been processed? */
3568 578142 : if (ts_stat->num_scanned == ts_stat->num_to_scan)
3569 : {
3570 3104 : binaryheap_remove_first(ts_heap);
3571 : }
3572 : else
3573 : {
3574 : /* update heap with the new progress */
3575 575038 : binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
3576 : }
3577 :
3578 : /*
3579 : * Sleep to throttle our I/O rate.
3580 : *
3581 : * (This will check for barrier events even if it doesn't sleep.)
3582 : */
3583 578142 : CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
3584 : }
3585 :
3586 : /*
3587 : * Issue all pending flushes. Only checkpointer calls BufferSync(), so
3588 : * IOContext will always be IOCONTEXT_NORMAL.
3589 : */
3590 2076 : IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
3591 :
3592 2076 : pfree(per_ts_stat);
3593 2076 : per_ts_stat = NULL;
3594 2076 : binaryheap_free(ts_heap);
3595 :
3596 : /*
3597 : * Update checkpoint statistics. As noted above, this doesn't include
3598 : * buffers written by other backends or bgwriter scan.
3599 : */
3600 2076 : CheckpointStats.ckpt_bufs_written += num_written;
3601 :
3602 : TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
3603 : }
3604 :
3605 : /*
3606 : * BgBufferSync -- Write out some dirty buffers in the pool.
3607 : *
3608 : * This is called periodically by the background writer process.
3609 : *
3610 : * Returns true if it's appropriate for the bgwriter process to go into
3611 : * low-power hibernation mode. (This happens if the strategy clock sweep
3612 : * has been "lapped" and no buffer allocations have occurred recently,
3613 : * or if the bgwriter has been effectively disabled by setting
3614 : * bgwriter_lru_maxpages to 0.)
3615 : */
3616 : bool
3617 22376 : BgBufferSync(WritebackContext *wb_context)
3618 : {
3619 : /* info obtained from freelist.c */
3620 : int strategy_buf_id;
3621 : uint32 strategy_passes;
3622 : uint32 recent_alloc;
3623 :
3624 : /*
3625 : * Information saved between calls so we can determine the strategy
3626 : * point's advance rate and avoid scanning already-cleaned buffers.
3627 : */
3628 : static bool saved_info_valid = false;
3629 : static int prev_strategy_buf_id;
3630 : static uint32 prev_strategy_passes;
3631 : static int next_to_clean;
3632 : static uint32 next_passes;
3633 :
3634 : /* Moving averages of allocation rate and clean-buffer density */
3635 : static float smoothed_alloc = 0;
3636 : static float smoothed_density = 10.0;
3637 :
3638 : /* Potentially these could be tunables, but for now, not */
3639 22376 : float smoothing_samples = 16;
3640 22376 : float scan_whole_pool_milliseconds = 120000.0;
3641 :
3642 : /* Used to compute how far we scan ahead */
3643 : long strategy_delta;
3644 : int bufs_to_lap;
3645 : int bufs_ahead;
3646 : float scans_per_alloc;
3647 : int reusable_buffers_est;
3648 : int upcoming_alloc_est;
3649 : int min_scan_buffers;
3650 :
3651 : /* Variables for the scanning loop proper */
3652 : int num_to_scan;
3653 : int num_written;
3654 : int reusable_buffers;
3655 :
3656 : /* Variables for final smoothed_density update */
3657 : long new_strategy_delta;
3658 : uint32 new_recent_alloc;
3659 :
3660 : /*
3661 : * Find out where the freelist clock sweep currently is, and how many
3662 : * buffer allocations have happened since our last call.
3663 : */
3664 22376 : strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
3665 :
3666 : /* Report buffer alloc counts to pgstat */
3667 22376 : PendingBgWriterStats.buf_alloc += recent_alloc;
3668 :
3669 : /*
3670 : * If we're not running the LRU scan, just stop after doing the stats
3671 : * stuff. We mark the saved state invalid so that we can recover sanely
3672 : * if LRU scan is turned back on later.
3673 : */
3674 22376 : if (bgwriter_lru_maxpages <= 0)
3675 : {
3676 74 : saved_info_valid = false;
3677 74 : return true;
3678 : }
3679 :
3680 : /*
3681 : * Compute strategy_delta = how many buffers have been scanned by the
3682 : * clock sweep since last time. If first time through, assume none. Then
3683 : * see if we are still ahead of the clock sweep, and if so, how many
3684 : * buffers we could scan before we'd catch up with it and "lap" it. Note:
3685 : * weird-looking coding of xxx_passes comparisons are to avoid bogus
3686 : * behavior when the passes counts wrap around.
3687 : */
3688 22302 : if (saved_info_valid)
3689 : {
3690 21276 : int32 passes_delta = strategy_passes - prev_strategy_passes;
3691 :
3692 21276 : strategy_delta = strategy_buf_id - prev_strategy_buf_id;
3693 21276 : strategy_delta += (long) passes_delta * NBuffers;
3694 :
3695 : Assert(strategy_delta >= 0);
3696 :
3697 21276 : if ((int32) (next_passes - strategy_passes) > 0)
3698 : {
3699 : /* we're one pass ahead of the strategy point */
3700 5102 : bufs_to_lap = strategy_buf_id - next_to_clean;
3701 : #ifdef BGW_DEBUG
3702 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3703 : next_passes, next_to_clean,
3704 : strategy_passes, strategy_buf_id,
3705 : strategy_delta, bufs_to_lap);
3706 : #endif
3707 : }
3708 16174 : else if (next_passes == strategy_passes &&
3709 12454 : next_to_clean >= strategy_buf_id)
3710 : {
3711 : /* on same pass, but ahead or at least not behind */
3712 12186 : bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
3713 : #ifdef BGW_DEBUG
3714 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3715 : next_passes, next_to_clean,
3716 : strategy_passes, strategy_buf_id,
3717 : strategy_delta, bufs_to_lap);
3718 : #endif
3719 : }
3720 : else
3721 : {
3722 : /*
3723 : * We're behind, so skip forward to the strategy point and start
3724 : * cleaning from there.
3725 : */
3726 : #ifdef BGW_DEBUG
3727 : elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
3728 : next_passes, next_to_clean,
3729 : strategy_passes, strategy_buf_id,
3730 : strategy_delta);
3731 : #endif
3732 3988 : next_to_clean = strategy_buf_id;
3733 3988 : next_passes = strategy_passes;
3734 3988 : bufs_to_lap = NBuffers;
3735 : }
3736 : }
3737 : else
3738 : {
3739 : /*
3740 : * Initializing at startup or after LRU scanning had been off. Always
3741 : * start at the strategy point.
3742 : */
3743 : #ifdef BGW_DEBUG
3744 : elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
3745 : strategy_passes, strategy_buf_id);
3746 : #endif
3747 1026 : strategy_delta = 0;
3748 1026 : next_to_clean = strategy_buf_id;
3749 1026 : next_passes = strategy_passes;
3750 1026 : bufs_to_lap = NBuffers;
3751 : }
3752 :
3753 : /* Update saved info for next time */
3754 22302 : prev_strategy_buf_id = strategy_buf_id;
3755 22302 : prev_strategy_passes = strategy_passes;
3756 22302 : saved_info_valid = true;
3757 :
3758 : /*
3759 : * Compute how many buffers had to be scanned for each new allocation, ie,
3760 : * 1/density of reusable buffers, and track a moving average of that.
3761 : *
3762 : * If the strategy point didn't move, we don't update the density estimate
3763 : */
3764 22302 : if (strategy_delta > 0 && recent_alloc > 0)
3765 : {
3766 5132 : scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
3767 5132 : smoothed_density += (scans_per_alloc - smoothed_density) /
3768 : smoothing_samples;
3769 : }
3770 :
3771 : /*
3772 : * Estimate how many reusable buffers there are between the current
3773 : * strategy point and where we've scanned ahead to, based on the smoothed
3774 : * density estimate.
3775 : */
3776 22302 : bufs_ahead = NBuffers - bufs_to_lap;
3777 22302 : reusable_buffers_est = (float) bufs_ahead / smoothed_density;
3778 :
3779 : /*
3780 : * Track a moving average of recent buffer allocations. Here, rather than
3781 : * a true average we want a fast-attack, slow-decline behavior: we
3782 : * immediately follow any increase.
3783 : */
3784 22302 : if (smoothed_alloc <= (float) recent_alloc)
3785 6672 : smoothed_alloc = recent_alloc;
3786 : else
3787 15630 : smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
3788 : smoothing_samples;
3789 :
3790 : /* Scale the estimate by a GUC to allow more aggressive tuning. */
3791 22302 : upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
3792 :
3793 : /*
3794 : * If recent_alloc remains at zero for many cycles, smoothed_alloc will
3795 : * eventually underflow to zero, and the underflows produce annoying
3796 : * kernel warnings on some platforms. Once upcoming_alloc_est has gone to
3797 : * zero, there's no point in tracking smaller and smaller values of
3798 : * smoothed_alloc, so just reset it to exactly zero to avoid this
3799 : * syndrome. It will pop back up as soon as recent_alloc increases.
3800 : */
3801 22302 : if (upcoming_alloc_est == 0)
3802 4132 : smoothed_alloc = 0;
3803 :
3804 : /*
3805 : * Even in cases where there's been little or no buffer allocation
3806 : * activity, we want to make a small amount of progress through the buffer
3807 : * cache so that as many reusable buffers as possible are clean after an
3808 : * idle period.
3809 : *
3810 : * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
3811 : * the BGW will be called during the scan_whole_pool time; slice the
3812 : * buffer pool into that many sections.
3813 : */
3814 22302 : min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
3815 :
3816 22302 : if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
3817 : {
3818 : #ifdef BGW_DEBUG
3819 : elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
3820 : upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
3821 : #endif
3822 10890 : upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
3823 : }
3824 :
3825 : /*
3826 : * Now write out dirty reusable buffers, working forward from the
3827 : * next_to_clean point, until we have lapped the strategy scan, or cleaned
3828 : * enough buffers to match our estimate of the next cycle's allocation
3829 : * requirements, or hit the bgwriter_lru_maxpages limit.
3830 : */
3831 :
3832 22302 : num_to_scan = bufs_to_lap;
3833 22302 : num_written = 0;
3834 22302 : reusable_buffers = reusable_buffers_est;
3835 :
3836 : /* Execute the LRU scan */
3837 3446330 : while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
3838 : {
3839 3424034 : int sync_state = SyncOneBuffer(next_to_clean, true,
3840 : wb_context);
3841 :
3842 3424034 : if (++next_to_clean >= NBuffers)
3843 : {
3844 4512 : next_to_clean = 0;
3845 4512 : next_passes++;
3846 : }
3847 3424034 : num_to_scan--;
3848 :
3849 3424034 : if (sync_state & BUF_WRITTEN)
3850 : {
3851 34514 : reusable_buffers++;
3852 34514 : if (++num_written >= bgwriter_lru_maxpages)
3853 : {
3854 6 : PendingBgWriterStats.maxwritten_clean++;
3855 6 : break;
3856 : }
3857 : }
3858 3389520 : else if (sync_state & BUF_REUSABLE)
3859 2499228 : reusable_buffers++;
3860 : }
3861 :
3862 22302 : PendingBgWriterStats.buf_written_clean += num_written;
3863 :
3864 : #ifdef BGW_DEBUG
3865 : elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d",
3866 : recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
3867 : smoothed_density, reusable_buffers_est, upcoming_alloc_est,
3868 : bufs_to_lap - num_to_scan,
3869 : num_written,
3870 : reusable_buffers - reusable_buffers_est);
3871 : #endif
3872 :
3873 : /*
3874 : * Consider the above scan as being like a new allocation scan.
3875 : * Characterize its density and update the smoothed one based on it. This
3876 : * effectively halves the moving average period in cases where both the
3877 : * strategy and the background writer are doing some useful scanning,
3878 : * which is helpful because a long memory isn't as desirable on the
3879 : * density estimates.
3880 : */
3881 22302 : new_strategy_delta = bufs_to_lap - num_to_scan;
3882 22302 : new_recent_alloc = reusable_buffers - reusable_buffers_est;
3883 22302 : if (new_strategy_delta > 0 && new_recent_alloc > 0)
3884 : {
3885 16458 : scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
3886 16458 : smoothed_density += (scans_per_alloc - smoothed_density) /
3887 : smoothing_samples;
3888 :
3889 : #ifdef BGW_DEBUG
3890 : elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
3891 : new_recent_alloc, new_strategy_delta,
3892 : scans_per_alloc, smoothed_density);
3893 : #endif
3894 : }
3895 :
3896 : /* Return true if OK to hibernate */
3897 22302 : return (bufs_to_lap == 0 && recent_alloc == 0);
3898 : }
3899 :
3900 : /*
3901 : * SyncOneBuffer -- process a single buffer during syncing.
3902 : *
3903 : * If skip_recently_used is true, we don't write currently-pinned buffers, nor
3904 : * buffers marked recently used, as these are not replacement candidates.
3905 : *
3906 : * Returns a bitmask containing the following flag bits:
3907 : * BUF_WRITTEN: we wrote the buffer.
3908 : * BUF_REUSABLE: buffer is available for replacement, ie, it has
3909 : * pin count 0 and usage count 0.
3910 : *
3911 : * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
3912 : * after locking it, but we don't care all that much.)
3913 : */
3914 : static int
3915 3964538 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
3916 : {
3917 3964538 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
3918 3964538 : int result = 0;
3919 : uint32 buf_state;
3920 : BufferTag tag;
3921 :
3922 : /* Make sure we can handle the pin */
3923 3964538 : ReservePrivateRefCountEntry();
3924 3964538 : ResourceOwnerEnlarge(CurrentResourceOwner);
3925 :
3926 : /*
3927 : * Check whether buffer needs writing.
3928 : *
3929 : * We can make this check without taking the buffer content lock so long
3930 : * as we mark pages dirty in access methods *before* logging changes with
3931 : * XLogInsert(): if someone marks the buffer dirty just after our check we
3932 : * don't worry because our checkpoint.redo points before log record for
3933 : * upcoming changes and so we are not required to write such dirty buffer.
3934 : */
3935 3964538 : buf_state = LockBufHdr(bufHdr);
3936 :
3937 3964538 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
3938 3956474 : BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
3939 : {
3940 2537294 : result |= BUF_REUSABLE;
3941 : }
3942 1427244 : else if (skip_recently_used)
3943 : {
3944 : /* Caller told us not to write recently-used buffers */
3945 890292 : UnlockBufHdr(bufHdr, buf_state);
3946 890292 : return result;
3947 : }
3948 :
3949 3074246 : if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
3950 : {
3951 : /* It's clean, so nothing to do */
3952 2499228 : UnlockBufHdr(bufHdr, buf_state);
3953 2499228 : return result;
3954 : }
3955 :
3956 : /*
3957 : * Pin it, share-lock it, write it. (FlushBuffer will do nothing if the
3958 : * buffer is clean by the time we've locked it.)
3959 : */
3960 575018 : PinBuffer_Locked(bufHdr);
3961 575018 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3962 :
3963 575018 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
3964 :
3965 575018 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3966 :
3967 575018 : tag = bufHdr->tag;
3968 :
3969 575018 : UnpinBuffer(bufHdr);
3970 :
3971 : /*
3972 : * SyncOneBuffer() is only called by checkpointer and bgwriter, so
3973 : * IOContext will always be IOCONTEXT_NORMAL.
3974 : */
3975 575018 : ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
3976 :
3977 575018 : return result | BUF_WRITTEN;
3978 : }
3979 :
3980 : /*
3981 : * AtEOXact_Buffers - clean up at end of transaction.
3982 : *
3983 : * As of PostgreSQL 8.0, buffer pins should get released by the
3984 : * ResourceOwner mechanism. This routine is just a debugging
3985 : * cross-check that no pins remain.
3986 : */
3987 : void
3988 1054934 : AtEOXact_Buffers(bool isCommit)
3989 : {
3990 1054934 : CheckForBufferLeaks();
3991 :
3992 1054934 : AtEOXact_LocalBuffers(isCommit);
3993 :
3994 : Assert(PrivateRefCountOverflowed == 0);
3995 1054934 : }
3996 :
3997 : /*
3998 : * Initialize access to shared buffer pool
3999 : *
4000 : * This is called during backend startup (whether standalone or under the
4001 : * postmaster). It sets up for this backend's access to the already-existing
4002 : * buffer pool.
4003 : */
4004 : void
4005 43234 : InitBufferManagerAccess(void)
4006 : {
4007 : HASHCTL hash_ctl;
4008 :
4009 : /*
4010 : * An advisory limit on the number of pins each backend should hold, based
4011 : * on shared_buffers and the maximum number of connections possible.
4012 : * That's very pessimistic, but outside toy-sized shared_buffers it should
4013 : * allow plenty of pins. LimitAdditionalPins() and
4014 : * GetAdditionalPinLimit() can be used to check the remaining balance.
4015 : */
4016 43234 : MaxProportionalPins = NBuffers / (MaxBackends + NUM_AUXILIARY_PROCS);
4017 :
4018 43234 : memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
4019 :
4020 43234 : hash_ctl.keysize = sizeof(int32);
4021 43234 : hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
4022 :
4023 43234 : PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
4024 : HASH_ELEM | HASH_BLOBS);
4025 :
4026 : /*
4027 : * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
4028 : * the corresponding phase of backend shutdown.
4029 : */
4030 : Assert(MyProc != NULL);
4031 43234 : on_shmem_exit(AtProcExit_Buffers, 0);
4032 43234 : }
4033 :
4034 : /*
4035 : * During backend exit, ensure that we released all shared-buffer locks and
4036 : * assert that we have no remaining pins.
4037 : */
4038 : static void
4039 43234 : AtProcExit_Buffers(int code, Datum arg)
4040 : {
4041 43234 : UnlockBuffers();
4042 :
4043 43234 : CheckForBufferLeaks();
4044 :
4045 : /* localbuf.c needs a chance too */
4046 43234 : AtProcExit_LocalBuffers();
4047 43234 : }
4048 :
4049 : /*
4050 : * CheckForBufferLeaks - ensure this backend holds no buffer pins
4051 : *
4052 : * As of PostgreSQL 8.0, buffer pins should get released by the
4053 : * ResourceOwner mechanism. This routine is just a debugging
4054 : * cross-check that no pins remain.
4055 : */
4056 : static void
4057 1098168 : CheckForBufferLeaks(void)
4058 : {
4059 : #ifdef USE_ASSERT_CHECKING
4060 : int RefCountErrors = 0;
4061 : PrivateRefCountEntry *res;
4062 : int i;
4063 : char *s;
4064 :
4065 : /* check the array */
4066 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
4067 : {
4068 : res = &PrivateRefCountArray[i];
4069 :
4070 : if (res->buffer != InvalidBuffer)
4071 : {
4072 : s = DebugPrintBufferRefcount(res->buffer);
4073 : elog(WARNING, "buffer refcount leak: %s", s);
4074 : pfree(s);
4075 :
4076 : RefCountErrors++;
4077 : }
4078 : }
4079 :
4080 : /* if necessary search the hash */
4081 : if (PrivateRefCountOverflowed)
4082 : {
4083 : HASH_SEQ_STATUS hstat;
4084 :
4085 : hash_seq_init(&hstat, PrivateRefCountHash);
4086 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
4087 : {
4088 : s = DebugPrintBufferRefcount(res->buffer);
4089 : elog(WARNING, "buffer refcount leak: %s", s);
4090 : pfree(s);
4091 : RefCountErrors++;
4092 : }
4093 : }
4094 :
4095 : Assert(RefCountErrors == 0);
4096 : #endif
4097 1098168 : }
4098 :
4099 : #ifdef USE_ASSERT_CHECKING
4100 : /*
4101 : * Check for exclusive-locked catalog buffers. This is the core of
4102 : * AssertCouldGetRelation().
4103 : *
4104 : * A backend would self-deadlock on LWLocks if the catalog scan read the
4105 : * exclusive-locked buffer. The main threat is exclusive-locked buffers of
4106 : * catalogs used in relcache, because a catcache search on any catalog may
4107 : * build that catalog's relcache entry. We don't have an inventory of
4108 : * catalogs relcache uses, so just check buffers of most catalogs.
4109 : *
4110 : * It's better to minimize waits while holding an exclusive buffer lock, so it
4111 : * would be nice to broaden this check not to be catalog-specific. However,
4112 : * bttextcmp() accesses pg_collation, and non-core opclasses might similarly
4113 : * read tables. That is deadlock-free as long as there's no loop in the
4114 : * dependency graph: modifying table A may cause an opclass to read table B,
4115 : * but it must not cause a read of table A.
4116 : */
4117 : void
4118 : AssertBufferLocksPermitCatalogRead(void)
4119 : {
4120 : ForEachLWLockHeldByMe(AssertNotCatalogBufferLock, NULL);
4121 : }
4122 :
4123 : static void
4124 : AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
4125 : void *unused_context)
4126 : {
4127 : BufferDesc *bufHdr;
4128 : BufferTag tag;
4129 : Oid relid;
4130 :
4131 : if (mode != LW_EXCLUSIVE)
4132 : return;
4133 :
4134 : if (!((BufferDescPadded *) lock > BufferDescriptors &&
4135 : (BufferDescPadded *) lock < BufferDescriptors + NBuffers))
4136 : return; /* not a buffer lock */
4137 :
4138 : bufHdr = (BufferDesc *)
4139 : ((char *) lock - offsetof(BufferDesc, content_lock));
4140 : tag = bufHdr->tag;
4141 :
4142 : /*
4143 : * This relNumber==relid assumption holds until a catalog experiences
4144 : * VACUUM FULL or similar. After a command like that, relNumber will be
4145 : * in the normal (non-catalog) range, and we lose the ability to detect
4146 : * hazardous access to that catalog. Calling RelidByRelfilenumber() would
4147 : * close that gap, but RelidByRelfilenumber() might then deadlock with a
4148 : * held lock.
4149 : */
4150 : relid = tag.relNumber;
4151 :
4152 : if (IsCatalogTextUniqueIndexOid(relid)) /* see comments at the callee */
4153 : return;
4154 :
4155 : Assert(!IsCatalogRelationOid(relid));
4156 : }
4157 : #endif
4158 :
4159 :
4160 : /*
4161 : * Helper routine to issue warnings when a buffer is unexpectedly pinned
4162 : */
4163 : char *
4164 80 : DebugPrintBufferRefcount(Buffer buffer)
4165 : {
4166 : BufferDesc *buf;
4167 : int32 loccount;
4168 : char *result;
4169 : ProcNumber backend;
4170 : uint32 buf_state;
4171 :
4172 : Assert(BufferIsValid(buffer));
4173 80 : if (BufferIsLocal(buffer))
4174 : {
4175 32 : buf = GetLocalBufferDescriptor(-buffer - 1);
4176 32 : loccount = LocalRefCount[-buffer - 1];
4177 32 : backend = MyProcNumber;
4178 : }
4179 : else
4180 : {
4181 48 : buf = GetBufferDescriptor(buffer - 1);
4182 48 : loccount = GetPrivateRefCount(buffer);
4183 48 : backend = INVALID_PROC_NUMBER;
4184 : }
4185 :
4186 : /* theoretically we should lock the bufhdr here */
4187 80 : buf_state = pg_atomic_read_u32(&buf->state);
4188 :
4189 80 : result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
4190 : buffer,
4191 80 : relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
4192 : BufTagGetForkNum(&buf->tag)).str,
4193 : buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
4194 : BUF_STATE_GET_REFCOUNT(buf_state), loccount);
4195 80 : return result;
4196 : }
4197 :
4198 : /*
4199 : * CheckPointBuffers
4200 : *
4201 : * Flush all dirty blocks in buffer pool to disk at checkpoint time.
4202 : *
4203 : * Note: temporary relations do not participate in checkpoints, so they don't
4204 : * need to be flushed.
4205 : */
4206 : void
4207 3362 : CheckPointBuffers(int flags)
4208 : {
4209 3362 : BufferSync(flags);
4210 3362 : }
4211 :
4212 : /*
4213 : * BufferGetBlockNumber
4214 : * Returns the block number associated with a buffer.
4215 : *
4216 : * Note:
4217 : * Assumes that the buffer is valid and pinned, else the
4218 : * value may be obsolete immediately...
4219 : */
4220 : BlockNumber
4221 99278504 : BufferGetBlockNumber(Buffer buffer)
4222 : {
4223 : BufferDesc *bufHdr;
4224 :
4225 : Assert(BufferIsPinned(buffer));
4226 :
4227 99278504 : if (BufferIsLocal(buffer))
4228 3809048 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
4229 : else
4230 95469456 : bufHdr = GetBufferDescriptor(buffer - 1);
4231 :
4232 : /* pinned, so OK to read tag without spinlock */
4233 99278504 : return bufHdr->tag.blockNum;
4234 : }
4235 :
4236 : /*
4237 : * BufferGetTag
4238 : * Returns the relfilelocator, fork number and block number associated with
4239 : * a buffer.
4240 : */
4241 : void
4242 29977504 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
4243 : BlockNumber *blknum)
4244 : {
4245 : BufferDesc *bufHdr;
4246 :
4247 : /* Do the same checks as BufferGetBlockNumber. */
4248 : Assert(BufferIsPinned(buffer));
4249 :
4250 29977504 : if (BufferIsLocal(buffer))
4251 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
4252 : else
4253 29977504 : bufHdr = GetBufferDescriptor(buffer - 1);
4254 :
4255 : /* pinned, so OK to read tag without spinlock */
4256 29977504 : *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
4257 29977504 : *forknum = BufTagGetForkNum(&bufHdr->tag);
4258 29977504 : *blknum = bufHdr->tag.blockNum;
4259 29977504 : }
4260 :
4261 : /*
4262 : * FlushBuffer
4263 : * Physically write out a shared buffer.
4264 : *
4265 : * NOTE: this actually just passes the buffer contents to the kernel; the
4266 : * real write to disk won't happen until the kernel feels like it. This
4267 : * is okay from our point of view since we can redo the changes from WAL.
4268 : * However, we will need to force the changes to disk via fsync before
4269 : * we can checkpoint WAL.
4270 : *
4271 : * The caller must hold a pin on the buffer and have share-locked the
4272 : * buffer contents. (Note: a share-lock does not prevent updates of
4273 : * hint bits in the buffer, so the page could change while the write
4274 : * is in progress, but we assume that that will not invalidate the data
4275 : * written.)
4276 : *
4277 : * If the caller has an smgr reference for the buffer's relation, pass it
4278 : * as the second parameter. If not, pass NULL.
4279 : */
4280 : static void
4281 1098980 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
4282 : IOContext io_context)
4283 : {
4284 : XLogRecPtr recptr;
4285 : ErrorContextCallback errcallback;
4286 : instr_time io_start;
4287 : Block bufBlock;
4288 : char *bufToWrite;
4289 : uint32 buf_state;
4290 :
4291 : /*
4292 : * Try to start an I/O operation. If StartBufferIO returns false, then
4293 : * someone else flushed the buffer before we could, so we need not do
4294 : * anything.
4295 : */
4296 1098980 : if (!StartBufferIO(buf, false, false))
4297 14 : return;
4298 :
4299 : /* Setup error traceback support for ereport() */
4300 1098966 : errcallback.callback = shared_buffer_write_error_callback;
4301 1098966 : errcallback.arg = buf;
4302 1098966 : errcallback.previous = error_context_stack;
4303 1098966 : error_context_stack = &errcallback;
4304 :
4305 : /* Find smgr relation for buffer */
4306 1098966 : if (reln == NULL)
4307 1090692 : reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
4308 :
4309 : TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
4310 : buf->tag.blockNum,
4311 : reln->smgr_rlocator.locator.spcOid,
4312 : reln->smgr_rlocator.locator.dbOid,
4313 : reln->smgr_rlocator.locator.relNumber);
4314 :
4315 1098966 : buf_state = LockBufHdr(buf);
4316 :
4317 : /*
4318 : * Run PageGetLSN while holding header lock, since we don't have the
4319 : * buffer locked exclusively in all cases.
4320 : */
4321 1098966 : recptr = BufferGetLSN(buf);
4322 :
4323 : /* To check if block content changes while flushing. - vadim 01/17/97 */
4324 1098966 : buf_state &= ~BM_JUST_DIRTIED;
4325 1098966 : UnlockBufHdr(buf, buf_state);
4326 :
4327 : /*
4328 : * Force XLOG flush up to buffer's LSN. This implements the basic WAL
4329 : * rule that log updates must hit disk before any of the data-file changes
4330 : * they describe do.
4331 : *
4332 : * However, this rule does not apply to unlogged relations, which will be
4333 : * lost after a crash anyway. Most unlogged relation pages do not bear
4334 : * LSNs since we never emit WAL records for them, and therefore flushing
4335 : * up through the buffer LSN would be useless, but harmless. However,
4336 : * GiST indexes use LSNs internally to track page-splits, and therefore
4337 : * unlogged GiST pages bear "fake" LSNs generated by
4338 : * GetFakeLSNForUnloggedRel. It is unlikely but possible that the fake
4339 : * LSN counter could advance past the WAL insertion point; and if it did
4340 : * happen, attempting to flush WAL through that location would fail, with
4341 : * disastrous system-wide consequences. To make sure that can't happen,
4342 : * skip the flush if the buffer isn't permanent.
4343 : */
4344 1098966 : if (buf_state & BM_PERMANENT)
4345 1095410 : XLogFlush(recptr);
4346 :
4347 : /*
4348 : * Now it's safe to write the buffer to disk. Note that no one else should
4349 : * have been able to write it, while we were busy with log flushing,
4350 : * because we got the exclusive right to perform I/O by setting the
4351 : * BM_IO_IN_PROGRESS bit.
4352 : */
4353 1098966 : bufBlock = BufHdrGetBlock(buf);
4354 :
4355 : /*
4356 : * Update page checksum if desired. Since we have only shared lock on the
4357 : * buffer, other processes might be updating hint bits in it, so we must
4358 : * copy the page to private storage if we do checksumming.
4359 : */
4360 1098966 : bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
4361 :
4362 1098966 : io_start = pgstat_prepare_io_time(track_io_timing);
4363 :
4364 : /*
4365 : * bufToWrite is either the shared buffer or a copy, as appropriate.
4366 : */
4367 1098966 : smgrwrite(reln,
4368 1098966 : BufTagGetForkNum(&buf->tag),
4369 : buf->tag.blockNum,
4370 : bufToWrite,
4371 : false);
4372 :
4373 : /*
4374 : * When a strategy is in use, only flushes of dirty buffers already in the
4375 : * strategy ring are counted as strategy writes (IOCONTEXT
4376 : * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
4377 : * statistics tracking.
4378 : *
4379 : * If a shared buffer initially added to the ring must be flushed before
4380 : * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
4381 : *
4382 : * If a shared buffer which was added to the ring later because the
4383 : * current strategy buffer is pinned or in use or because all strategy
4384 : * buffers were dirty and rejected (for BAS_BULKREAD operations only)
4385 : * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
4386 : * (from_ring will be false).
4387 : *
4388 : * When a strategy is not in use, the write can only be a "regular" write
4389 : * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
4390 : */
4391 1098966 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
4392 : IOOP_WRITE, io_start, 1, BLCKSZ);
4393 :
4394 1098966 : pgBufferUsage.shared_blks_written++;
4395 :
4396 : /*
4397 : * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
4398 : * end the BM_IO_IN_PROGRESS state.
4399 : */
4400 1098966 : TerminateBufferIO(buf, true, 0, true, false);
4401 :
4402 : TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
4403 : buf->tag.blockNum,
4404 : reln->smgr_rlocator.locator.spcOid,
4405 : reln->smgr_rlocator.locator.dbOid,
4406 : reln->smgr_rlocator.locator.relNumber);
4407 :
4408 : /* Pop the error context stack */
4409 1098966 : error_context_stack = errcallback.previous;
4410 : }
4411 :
4412 : /*
4413 : * RelationGetNumberOfBlocksInFork
4414 : * Determines the current number of pages in the specified relation fork.
4415 : *
4416 : * Note that the accuracy of the result will depend on the details of the
4417 : * relation's storage. For builtin AMs it'll be accurate, but for external AMs
4418 : * it might not be.
4419 : */
4420 : BlockNumber
4421 3646076 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
4422 : {
4423 3646076 : if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
4424 : {
4425 : /*
4426 : * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
4427 : * tableam returns the size in bytes - but for the purpose of this
4428 : * routine, we want the number of blocks. Therefore divide, rounding
4429 : * up.
4430 : */
4431 : uint64 szbytes;
4432 :
4433 2773724 : szbytes = table_relation_size(relation, forkNum);
4434 :
4435 2773686 : return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
4436 : }
4437 872352 : else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
4438 : {
4439 872352 : return smgrnblocks(RelationGetSmgr(relation), forkNum);
4440 : }
4441 : else
4442 : Assert(false);
4443 :
4444 0 : return 0; /* keep compiler quiet */
4445 : }
4446 :
4447 : /*
4448 : * BufferIsPermanent
4449 : * Determines whether a buffer will potentially still be around after
4450 : * a crash. Caller must hold a buffer pin.
4451 : */
4452 : bool
4453 19039208 : BufferIsPermanent(Buffer buffer)
4454 : {
4455 : BufferDesc *bufHdr;
4456 :
4457 : /* Local buffers are used only for temp relations. */
4458 19039208 : if (BufferIsLocal(buffer))
4459 1253868 : return false;
4460 :
4461 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
4462 : Assert(BufferIsValid(buffer));
4463 : Assert(BufferIsPinned(buffer));
4464 :
4465 : /*
4466 : * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
4467 : * need not bother with the buffer header spinlock. Even if someone else
4468 : * changes the buffer header state while we're doing this, the state is
4469 : * changed atomically, so we'll read the old value or the new value, but
4470 : * not random garbage.
4471 : */
4472 17785340 : bufHdr = GetBufferDescriptor(buffer - 1);
4473 17785340 : return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
4474 : }
4475 :
4476 : /*
4477 : * BufferGetLSNAtomic
4478 : * Retrieves the LSN of the buffer atomically using a buffer header lock.
4479 : * This is necessary for some callers who may not have an exclusive lock
4480 : * on the buffer.
4481 : */
4482 : XLogRecPtr
4483 13825890 : BufferGetLSNAtomic(Buffer buffer)
4484 : {
4485 13825890 : char *page = BufferGetPage(buffer);
4486 : BufferDesc *bufHdr;
4487 : XLogRecPtr lsn;
4488 : uint32 buf_state;
4489 :
4490 : /*
4491 : * If we don't need locking for correctness, fastpath out.
4492 : */
4493 13825890 : if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
4494 477378 : return PageGetLSN(page);
4495 :
4496 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
4497 : Assert(BufferIsValid(buffer));
4498 : Assert(BufferIsPinned(buffer));
4499 :
4500 13348512 : bufHdr = GetBufferDescriptor(buffer - 1);
4501 13348512 : buf_state = LockBufHdr(bufHdr);
4502 13348512 : lsn = PageGetLSN(page);
4503 13348512 : UnlockBufHdr(bufHdr, buf_state);
4504 :
4505 13348512 : return lsn;
4506 : }
4507 :
4508 : /* ---------------------------------------------------------------------
4509 : * DropRelationBuffers
4510 : *
4511 : * This function removes from the buffer pool all the pages of the
4512 : * specified relation forks that have block numbers >= firstDelBlock.
4513 : * (In particular, with firstDelBlock = 0, all pages are removed.)
4514 : * Dirty pages are simply dropped, without bothering to write them
4515 : * out first. Therefore, this is NOT rollback-able, and so should be
4516 : * used only with extreme caution!
4517 : *
4518 : * Currently, this is called only from smgr.c when the underlying file
4519 : * is about to be deleted or truncated (firstDelBlock is needed for
4520 : * the truncation case). The data in the affected pages would therefore
4521 : * be deleted momentarily anyway, and there is no point in writing it.
4522 : * It is the responsibility of higher-level code to ensure that the
4523 : * deletion or truncation does not lose any data that could be needed
4524 : * later. It is also the responsibility of higher-level code to ensure
4525 : * that no other process could be trying to load more pages of the
4526 : * relation into buffers.
4527 : * --------------------------------------------------------------------
4528 : */
4529 : void
4530 1270 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
4531 : int nforks, BlockNumber *firstDelBlock)
4532 : {
4533 : int i;
4534 : int j;
4535 : RelFileLocatorBackend rlocator;
4536 : BlockNumber nForkBlock[MAX_FORKNUM];
4537 1270 : uint64 nBlocksToInvalidate = 0;
4538 :
4539 1270 : rlocator = smgr_reln->smgr_rlocator;
4540 :
4541 : /* If it's a local relation, it's localbuf.c's problem. */
4542 1270 : if (RelFileLocatorBackendIsTemp(rlocator))
4543 : {
4544 748 : if (rlocator.backend == MyProcNumber)
4545 748 : DropRelationLocalBuffers(rlocator.locator, forkNum, nforks,
4546 : firstDelBlock);
4547 :
4548 832 : return;
4549 : }
4550 :
4551 : /*
4552 : * To remove all the pages of the specified relation forks from the buffer
4553 : * pool, we need to scan the entire buffer pool but we can optimize it by
4554 : * finding the buffers from BufMapping table provided we know the exact
4555 : * size of each fork of the relation. The exact size is required to ensure
4556 : * that we don't leave any buffer for the relation being dropped as
4557 : * otherwise the background writer or checkpointer can lead to a PANIC
4558 : * error while flushing buffers corresponding to files that don't exist.
4559 : *
4560 : * To know the exact size, we rely on the size cached for each fork by us
4561 : * during recovery which limits the optimization to recovery and on
4562 : * standbys but we can easily extend it once we have shared cache for
4563 : * relation size.
4564 : *
4565 : * In recovery, we cache the value returned by the first lseek(SEEK_END)
4566 : * and the future writes keeps the cached value up-to-date. See
4567 : * smgrextend. It is possible that the value of the first lseek is smaller
4568 : * than the actual number of existing blocks in the file due to buggy
4569 : * Linux kernels that might not have accounted for the recent write. But
4570 : * that should be fine because there must not be any buffers after that
4571 : * file size.
4572 : */
4573 722 : for (i = 0; i < nforks; i++)
4574 : {
4575 : /* Get the number of blocks for a relation's fork */
4576 614 : nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
4577 :
4578 614 : if (nForkBlock[i] == InvalidBlockNumber)
4579 : {
4580 414 : nBlocksToInvalidate = InvalidBlockNumber;
4581 414 : break;
4582 : }
4583 :
4584 : /* calculate the number of blocks to be invalidated */
4585 200 : nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
4586 : }
4587 :
4588 : /*
4589 : * We apply the optimization iff the total number of blocks to invalidate
4590 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4591 : */
4592 522 : if (BlockNumberIsValid(nBlocksToInvalidate) &&
4593 108 : nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4594 : {
4595 232 : for (j = 0; j < nforks; j++)
4596 148 : FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
4597 148 : nForkBlock[j], firstDelBlock[j]);
4598 84 : return;
4599 : }
4600 :
4601 5648566 : for (i = 0; i < NBuffers; i++)
4602 : {
4603 5648128 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4604 : uint32 buf_state;
4605 :
4606 : /*
4607 : * We can make this a tad faster by prechecking the buffer tag before
4608 : * we attempt to lock the buffer; this saves a lot of lock
4609 : * acquisitions in typical cases. It should be safe because the
4610 : * caller must have AccessExclusiveLock on the relation, or some other
4611 : * reason to be certain that no one is loading new pages of the rel
4612 : * into the buffer pool. (Otherwise we might well miss such pages
4613 : * entirely.) Therefore, while the tag might be changing while we
4614 : * look at it, it can't be changing *to* a value we care about, only
4615 : * *away* from such a value. So false negatives are impossible, and
4616 : * false positives are safe because we'll recheck after getting the
4617 : * buffer lock.
4618 : *
4619 : * We could check forkNum and blockNum as well as the rlocator, but
4620 : * the incremental win from doing so seems small.
4621 : */
4622 5648128 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
4623 5634134 : continue;
4624 :
4625 13994 : buf_state = LockBufHdr(bufHdr);
4626 :
4627 36116 : for (j = 0; j < nforks; j++)
4628 : {
4629 25316 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
4630 25316 : BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
4631 13798 : bufHdr->tag.blockNum >= firstDelBlock[j])
4632 : {
4633 3194 : InvalidateBuffer(bufHdr); /* releases spinlock */
4634 3194 : break;
4635 : }
4636 : }
4637 13994 : if (j >= nforks)
4638 10800 : UnlockBufHdr(bufHdr, buf_state);
4639 : }
4640 : }
4641 :
4642 : /* ---------------------------------------------------------------------
4643 : * DropRelationsAllBuffers
4644 : *
4645 : * This function removes from the buffer pool all the pages of all
4646 : * forks of the specified relations. It's equivalent to calling
4647 : * DropRelationBuffers once per fork per relation with firstDelBlock = 0.
4648 : * --------------------------------------------------------------------
4649 : */
4650 : void
4651 26768 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
4652 : {
4653 : int i;
4654 26768 : int n = 0;
4655 : SMgrRelation *rels;
4656 : BlockNumber (*block)[MAX_FORKNUM + 1];
4657 26768 : uint64 nBlocksToInvalidate = 0;
4658 : RelFileLocator *locators;
4659 26768 : bool cached = true;
4660 : bool use_bsearch;
4661 :
4662 26768 : if (nlocators == 0)
4663 0 : return;
4664 :
4665 26768 : rels = palloc(sizeof(SMgrRelation) * nlocators); /* non-local relations */
4666 :
4667 : /* If it's a local relation, it's localbuf.c's problem. */
4668 117242 : for (i = 0; i < nlocators; i++)
4669 : {
4670 90474 : if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
4671 : {
4672 6264 : if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
4673 6264 : DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
4674 : }
4675 : else
4676 84210 : rels[n++] = smgr_reln[i];
4677 : }
4678 :
4679 : /*
4680 : * If there are no non-local relations, then we're done. Release the
4681 : * memory and return.
4682 : */
4683 26768 : if (n == 0)
4684 : {
4685 1606 : pfree(rels);
4686 1606 : return;
4687 : }
4688 :
4689 : /*
4690 : * This is used to remember the number of blocks for all the relations
4691 : * forks.
4692 : */
4693 : block = (BlockNumber (*)[MAX_FORKNUM + 1])
4694 25162 : palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
4695 :
4696 : /*
4697 : * We can avoid scanning the entire buffer pool if we know the exact size
4698 : * of each of the given relation forks. See DropRelationBuffers.
4699 : */
4700 53012 : for (i = 0; i < n && cached; i++)
4701 : {
4702 45332 : for (int j = 0; j <= MAX_FORKNUM; j++)
4703 : {
4704 : /* Get the number of blocks for a relation's fork. */
4705 40984 : block[i][j] = smgrnblocks_cached(rels[i], j);
4706 :
4707 : /* We need to only consider the relation forks that exists. */
4708 40984 : if (block[i][j] == InvalidBlockNumber)
4709 : {
4710 36238 : if (!smgrexists(rels[i], j))
4711 12736 : continue;
4712 23502 : cached = false;
4713 23502 : break;
4714 : }
4715 :
4716 : /* calculate the total number of blocks to be invalidated */
4717 4746 : nBlocksToInvalidate += block[i][j];
4718 : }
4719 : }
4720 :
4721 : /*
4722 : * We apply the optimization iff the total number of blocks to invalidate
4723 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4724 : */
4725 25162 : if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4726 : {
4727 2718 : for (i = 0; i < n; i++)
4728 : {
4729 7480 : for (int j = 0; j <= MAX_FORKNUM; j++)
4730 : {
4731 : /* ignore relation forks that doesn't exist */
4732 5984 : if (!BlockNumberIsValid(block[i][j]))
4733 4470 : continue;
4734 :
4735 : /* drop all the buffers for a particular relation fork */
4736 1514 : FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
4737 1514 : j, block[i][j], 0);
4738 : }
4739 : }
4740 :
4741 1222 : pfree(block);
4742 1222 : pfree(rels);
4743 1222 : return;
4744 : }
4745 :
4746 23940 : pfree(block);
4747 23940 : locators = palloc(sizeof(RelFileLocator) * n); /* non-local relations */
4748 106654 : for (i = 0; i < n; i++)
4749 82714 : locators[i] = rels[i]->smgr_rlocator.locator;
4750 :
4751 : /*
4752 : * For low number of relations to drop just use a simple walk through, to
4753 : * save the bsearch overhead. The threshold to use is rather a guess than
4754 : * an exactly determined value, as it depends on many factors (CPU and RAM
4755 : * speeds, amount of shared buffers etc.).
4756 : */
4757 23940 : use_bsearch = n > RELS_BSEARCH_THRESHOLD;
4758 :
4759 : /* sort the list of rlocators if necessary */
4760 23940 : if (use_bsearch)
4761 334 : qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
4762 :
4763 259900548 : for (i = 0; i < NBuffers; i++)
4764 : {
4765 259876608 : RelFileLocator *rlocator = NULL;
4766 259876608 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4767 : uint32 buf_state;
4768 :
4769 : /*
4770 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4771 : * saves some cycles.
4772 : */
4773 :
4774 259876608 : if (!use_bsearch)
4775 : {
4776 : int j;
4777 :
4778 1035927018 : for (j = 0; j < n; j++)
4779 : {
4780 779748382 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
4781 : {
4782 176436 : rlocator = &locators[j];
4783 176436 : break;
4784 : }
4785 : }
4786 : }
4787 : else
4788 : {
4789 : RelFileLocator locator;
4790 :
4791 3521536 : locator = BufTagGetRelFileLocator(&bufHdr->tag);
4792 3521536 : rlocator = bsearch(&locator,
4793 : locators, n, sizeof(RelFileLocator),
4794 : rlocator_comparator);
4795 : }
4796 :
4797 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
4798 259876608 : if (rlocator == NULL)
4799 259696740 : continue;
4800 :
4801 179868 : buf_state = LockBufHdr(bufHdr);
4802 179868 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
4803 179868 : InvalidateBuffer(bufHdr); /* releases spinlock */
4804 : else
4805 0 : UnlockBufHdr(bufHdr, buf_state);
4806 : }
4807 :
4808 23940 : pfree(locators);
4809 23940 : pfree(rels);
4810 : }
4811 :
4812 : /* ---------------------------------------------------------------------
4813 : * FindAndDropRelationBuffers
4814 : *
4815 : * This function performs look up in BufMapping table and removes from the
4816 : * buffer pool all the pages of the specified relation fork that has block
4817 : * number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
4818 : * pages are removed.)
4819 : * --------------------------------------------------------------------
4820 : */
4821 : static void
4822 1662 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
4823 : BlockNumber nForkBlock,
4824 : BlockNumber firstDelBlock)
4825 : {
4826 : BlockNumber curBlock;
4827 :
4828 4004 : for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
4829 : {
4830 : uint32 bufHash; /* hash value for tag */
4831 : BufferTag bufTag; /* identity of requested block */
4832 : LWLock *bufPartitionLock; /* buffer partition lock for it */
4833 : int buf_id;
4834 : BufferDesc *bufHdr;
4835 : uint32 buf_state;
4836 :
4837 : /* create a tag so we can lookup the buffer */
4838 2342 : InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
4839 :
4840 : /* determine its hash code and partition lock ID */
4841 2342 : bufHash = BufTableHashCode(&bufTag);
4842 2342 : bufPartitionLock = BufMappingPartitionLock(bufHash);
4843 :
4844 : /* Check that it is in the buffer pool. If not, do nothing. */
4845 2342 : LWLockAcquire(bufPartitionLock, LW_SHARED);
4846 2342 : buf_id = BufTableLookup(&bufTag, bufHash);
4847 2342 : LWLockRelease(bufPartitionLock);
4848 :
4849 2342 : if (buf_id < 0)
4850 282 : continue;
4851 :
4852 2060 : bufHdr = GetBufferDescriptor(buf_id);
4853 :
4854 : /*
4855 : * We need to lock the buffer header and recheck if the buffer is
4856 : * still associated with the same block because the buffer could be
4857 : * evicted by some other backend loading blocks for a different
4858 : * relation after we release lock on the BufMapping table.
4859 : */
4860 2060 : buf_state = LockBufHdr(bufHdr);
4861 :
4862 4120 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
4863 2060 : BufTagGetForkNum(&bufHdr->tag) == forkNum &&
4864 2060 : bufHdr->tag.blockNum >= firstDelBlock)
4865 2060 : InvalidateBuffer(bufHdr); /* releases spinlock */
4866 : else
4867 0 : UnlockBufHdr(bufHdr, buf_state);
4868 : }
4869 1662 : }
4870 :
4871 : /* ---------------------------------------------------------------------
4872 : * DropDatabaseBuffers
4873 : *
4874 : * This function removes all the buffers in the buffer cache for a
4875 : * particular database. Dirty pages are simply dropped, without
4876 : * bothering to write them out first. This is used when we destroy a
4877 : * database, to avoid trying to flush data to disk when the directory
4878 : * tree no longer exists. Implementation is pretty similar to
4879 : * DropRelationBuffers() which is for destroying just one relation.
4880 : * --------------------------------------------------------------------
4881 : */
4882 : void
4883 134 : DropDatabaseBuffers(Oid dbid)
4884 : {
4885 : int i;
4886 :
4887 : /*
4888 : * We needn't consider local buffers, since by assumption the target
4889 : * database isn't our own.
4890 : */
4891 :
4892 895110 : for (i = 0; i < NBuffers; i++)
4893 : {
4894 894976 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4895 : uint32 buf_state;
4896 :
4897 : /*
4898 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4899 : * saves some cycles.
4900 : */
4901 894976 : if (bufHdr->tag.dbOid != dbid)
4902 870360 : continue;
4903 :
4904 24616 : buf_state = LockBufHdr(bufHdr);
4905 24616 : if (bufHdr->tag.dbOid == dbid)
4906 24616 : InvalidateBuffer(bufHdr); /* releases spinlock */
4907 : else
4908 0 : UnlockBufHdr(bufHdr, buf_state);
4909 : }
4910 134 : }
4911 :
4912 : /* ---------------------------------------------------------------------
4913 : * FlushRelationBuffers
4914 : *
4915 : * This function writes all dirty pages of a relation out to disk
4916 : * (or more accurately, out to kernel disk buffers), ensuring that the
4917 : * kernel has an up-to-date view of the relation.
4918 : *
4919 : * Generally, the caller should be holding AccessExclusiveLock on the
4920 : * target relation to ensure that no other backend is busy dirtying
4921 : * more blocks of the relation; the effects can't be expected to last
4922 : * after the lock is released.
4923 : *
4924 : * XXX currently it sequentially searches the buffer pool, should be
4925 : * changed to more clever ways of searching. This routine is not
4926 : * used in any performance-critical code paths, so it's not worth
4927 : * adding additional overhead to normal paths to make it go faster.
4928 : * --------------------------------------------------------------------
4929 : */
4930 : void
4931 276 : FlushRelationBuffers(Relation rel)
4932 : {
4933 : int i;
4934 : BufferDesc *bufHdr;
4935 276 : SMgrRelation srel = RelationGetSmgr(rel);
4936 :
4937 276 : if (RelationUsesLocalBuffers(rel))
4938 : {
4939 1818 : for (i = 0; i < NLocBuffer; i++)
4940 : {
4941 : uint32 buf_state;
4942 :
4943 1800 : bufHdr = GetLocalBufferDescriptor(i);
4944 1800 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4945 600 : ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
4946 : (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4947 : {
4948 : ErrorContextCallback errcallback;
4949 :
4950 : /* Setup error traceback support for ereport() */
4951 600 : errcallback.callback = local_buffer_write_error_callback;
4952 600 : errcallback.arg = bufHdr;
4953 600 : errcallback.previous = error_context_stack;
4954 600 : error_context_stack = &errcallback;
4955 :
4956 : /* Make sure we can handle the pin */
4957 600 : ReservePrivateRefCountEntry();
4958 600 : ResourceOwnerEnlarge(CurrentResourceOwner);
4959 :
4960 : /*
4961 : * Pin/unpin mostly to make valgrind work, but it also seems
4962 : * like the right thing to do.
4963 : */
4964 600 : PinLocalBuffer(bufHdr, false);
4965 :
4966 :
4967 600 : FlushLocalBuffer(bufHdr, srel);
4968 :
4969 600 : UnpinLocalBuffer(BufferDescriptorGetBuffer(bufHdr));
4970 :
4971 : /* Pop the error context stack */
4972 600 : error_context_stack = errcallback.previous;
4973 : }
4974 : }
4975 :
4976 18 : return;
4977 : }
4978 :
4979 3024386 : for (i = 0; i < NBuffers; i++)
4980 : {
4981 : uint32 buf_state;
4982 :
4983 3024128 : bufHdr = GetBufferDescriptor(i);
4984 :
4985 : /*
4986 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4987 : * saves some cycles.
4988 : */
4989 3024128 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
4990 3023682 : continue;
4991 :
4992 : /* Make sure we can handle the pin */
4993 446 : ReservePrivateRefCountEntry();
4994 446 : ResourceOwnerEnlarge(CurrentResourceOwner);
4995 :
4996 446 : buf_state = LockBufHdr(bufHdr);
4997 446 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4998 446 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4999 : {
5000 360 : PinBuffer_Locked(bufHdr);
5001 360 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
5002 360 : FlushBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5003 360 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
5004 360 : UnpinBuffer(bufHdr);
5005 : }
5006 : else
5007 86 : UnlockBufHdr(bufHdr, buf_state);
5008 : }
5009 : }
5010 :
5011 : /* ---------------------------------------------------------------------
5012 : * FlushRelationsAllBuffers
5013 : *
5014 : * This function flushes out of the buffer pool all the pages of all
5015 : * forks of the specified smgr relations. It's equivalent to calling
5016 : * FlushRelationBuffers once per relation. The relations are assumed not
5017 : * to use local buffers.
5018 : * --------------------------------------------------------------------
5019 : */
5020 : void
5021 24 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
5022 : {
5023 : int i;
5024 : SMgrSortArray *srels;
5025 : bool use_bsearch;
5026 :
5027 24 : if (nrels == 0)
5028 0 : return;
5029 :
5030 : /* fill-in array for qsort */
5031 24 : srels = palloc(sizeof(SMgrSortArray) * nrels);
5032 :
5033 48 : for (i = 0; i < nrels; i++)
5034 : {
5035 : Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
5036 :
5037 24 : srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
5038 24 : srels[i].srel = smgrs[i];
5039 : }
5040 :
5041 : /*
5042 : * Save the bsearch overhead for low number of relations to sync. See
5043 : * DropRelationsAllBuffers for details.
5044 : */
5045 24 : use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
5046 :
5047 : /* sort the list of SMgrRelations if necessary */
5048 24 : if (use_bsearch)
5049 0 : qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
5050 :
5051 393240 : for (i = 0; i < NBuffers; i++)
5052 : {
5053 393216 : SMgrSortArray *srelent = NULL;
5054 393216 : BufferDesc *bufHdr = GetBufferDescriptor(i);
5055 : uint32 buf_state;
5056 :
5057 : /*
5058 : * As in DropRelationBuffers, an unlocked precheck should be safe and
5059 : * saves some cycles.
5060 : */
5061 :
5062 393216 : if (!use_bsearch)
5063 : {
5064 : int j;
5065 :
5066 777604 : for (j = 0; j < nrels; j++)
5067 : {
5068 393216 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
5069 : {
5070 8828 : srelent = &srels[j];
5071 8828 : break;
5072 : }
5073 : }
5074 : }
5075 : else
5076 : {
5077 : RelFileLocator rlocator;
5078 :
5079 0 : rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
5080 0 : srelent = bsearch(&rlocator,
5081 : srels, nrels, sizeof(SMgrSortArray),
5082 : rlocator_comparator);
5083 : }
5084 :
5085 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
5086 393216 : if (srelent == NULL)
5087 384388 : continue;
5088 :
5089 : /* Make sure we can handle the pin */
5090 8828 : ReservePrivateRefCountEntry();
5091 8828 : ResourceOwnerEnlarge(CurrentResourceOwner);
5092 :
5093 8828 : buf_state = LockBufHdr(bufHdr);
5094 8828 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
5095 8828 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5096 : {
5097 7914 : PinBuffer_Locked(bufHdr);
5098 7914 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
5099 7914 : FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5100 7914 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
5101 7914 : UnpinBuffer(bufHdr);
5102 : }
5103 : else
5104 914 : UnlockBufHdr(bufHdr, buf_state);
5105 : }
5106 :
5107 24 : pfree(srels);
5108 : }
5109 :
5110 : /* ---------------------------------------------------------------------
5111 : * RelationCopyStorageUsingBuffer
5112 : *
5113 : * Copy fork's data using bufmgr. Same as RelationCopyStorage but instead
5114 : * of using smgrread and smgrextend this will copy using bufmgr APIs.
5115 : *
5116 : * Refer comments atop CreateAndCopyRelationData() for details about
5117 : * 'permanent' parameter.
5118 : * --------------------------------------------------------------------
5119 : */
5120 : static void
5121 146068 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
5122 : RelFileLocator dstlocator,
5123 : ForkNumber forkNum, bool permanent)
5124 : {
5125 : Buffer srcBuf;
5126 : Buffer dstBuf;
5127 : Page srcPage;
5128 : Page dstPage;
5129 : bool use_wal;
5130 : BlockNumber nblocks;
5131 : BlockNumber blkno;
5132 : PGIOAlignedBlock buf;
5133 : BufferAccessStrategy bstrategy_src;
5134 : BufferAccessStrategy bstrategy_dst;
5135 : BlockRangeReadStreamPrivate p;
5136 : ReadStream *src_stream;
5137 : SMgrRelation src_smgr;
5138 :
5139 : /*
5140 : * In general, we want to write WAL whenever wal_level > 'minimal', but we
5141 : * can skip it when copying any fork of an unlogged relation other than
5142 : * the init fork.
5143 : */
5144 146068 : use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
5145 :
5146 : /* Get number of blocks in the source relation. */
5147 146068 : nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
5148 : forkNum);
5149 :
5150 : /* Nothing to copy; just return. */
5151 146068 : if (nblocks == 0)
5152 25478 : return;
5153 :
5154 : /*
5155 : * Bulk extend the destination relation of the same size as the source
5156 : * relation before starting to copy block by block.
5157 : */
5158 120590 : memset(buf.data, 0, BLCKSZ);
5159 120590 : smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
5160 : buf.data, true);
5161 :
5162 : /* This is a bulk operation, so use buffer access strategies. */
5163 120590 : bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
5164 120590 : bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
5165 :
5166 : /* Initialize streaming read */
5167 120590 : p.current_blocknum = 0;
5168 120590 : p.last_exclusive = nblocks;
5169 120590 : src_smgr = smgropen(srclocator, INVALID_PROC_NUMBER);
5170 :
5171 : /*
5172 : * It is safe to use batchmode as block_range_read_stream_cb takes no
5173 : * locks.
5174 : */
5175 120590 : src_stream = read_stream_begin_smgr_relation(READ_STREAM_FULL |
5176 : READ_STREAM_USE_BATCHING,
5177 : bstrategy_src,
5178 : src_smgr,
5179 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
5180 : forkNum,
5181 : block_range_read_stream_cb,
5182 : &p,
5183 : 0);
5184 :
5185 : /* Iterate over each block of the source relation file. */
5186 580936 : for (blkno = 0; blkno < nblocks; blkno++)
5187 : {
5188 460350 : CHECK_FOR_INTERRUPTS();
5189 :
5190 : /* Read block from source relation. */
5191 460350 : srcBuf = read_stream_next_buffer(src_stream, NULL);
5192 460346 : LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
5193 460346 : srcPage = BufferGetPage(srcBuf);
5194 :
5195 460346 : dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum,
5196 : BufferGetBlockNumber(srcBuf),
5197 : RBM_ZERO_AND_LOCK, bstrategy_dst,
5198 : permanent);
5199 460346 : dstPage = BufferGetPage(dstBuf);
5200 :
5201 460346 : START_CRIT_SECTION();
5202 :
5203 : /* Copy page data from the source to the destination. */
5204 460346 : memcpy(dstPage, srcPage, BLCKSZ);
5205 460346 : MarkBufferDirty(dstBuf);
5206 :
5207 : /* WAL-log the copied page. */
5208 460346 : if (use_wal)
5209 251836 : log_newpage_buffer(dstBuf, true);
5210 :
5211 460346 : END_CRIT_SECTION();
5212 :
5213 460346 : UnlockReleaseBuffer(dstBuf);
5214 460346 : UnlockReleaseBuffer(srcBuf);
5215 : }
5216 : Assert(read_stream_next_buffer(src_stream, NULL) == InvalidBuffer);
5217 120586 : read_stream_end(src_stream);
5218 :
5219 120586 : FreeAccessStrategy(bstrategy_src);
5220 120586 : FreeAccessStrategy(bstrategy_dst);
5221 : }
5222 :
5223 : /* ---------------------------------------------------------------------
5224 : * CreateAndCopyRelationData
5225 : *
5226 : * Create destination relation storage and copy all forks from the
5227 : * source relation to the destination.
5228 : *
5229 : * Pass permanent as true for permanent relations and false for
5230 : * unlogged relations. Currently this API is not supported for
5231 : * temporary relations.
5232 : * --------------------------------------------------------------------
5233 : */
5234 : void
5235 109800 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
5236 : RelFileLocator dst_rlocator, bool permanent)
5237 : {
5238 : char relpersistence;
5239 : SMgrRelation src_rel;
5240 : SMgrRelation dst_rel;
5241 :
5242 : /* Set the relpersistence. */
5243 109800 : relpersistence = permanent ?
5244 : RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
5245 :
5246 109800 : src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
5247 109800 : dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
5248 :
5249 : /*
5250 : * Create and copy all forks of the relation. During create database we
5251 : * have a separate cleanup mechanism which deletes complete database
5252 : * directory. Therefore, each individual relation doesn't need to be
5253 : * registered for cleanup.
5254 : */
5255 109800 : RelationCreateStorage(dst_rlocator, relpersistence, false);
5256 :
5257 : /* copy main fork. */
5258 109800 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
5259 : permanent);
5260 :
5261 : /* copy those extra forks that exist */
5262 109796 : for (ForkNumber forkNum = MAIN_FORKNUM + 1;
5263 439184 : forkNum <= MAX_FORKNUM; forkNum++)
5264 : {
5265 329388 : if (smgrexists(src_rel, forkNum))
5266 : {
5267 36268 : smgrcreate(dst_rel, forkNum, false);
5268 :
5269 : /*
5270 : * WAL log creation if the relation is persistent, or this is the
5271 : * init fork of an unlogged relation.
5272 : */
5273 36268 : if (permanent || forkNum == INIT_FORKNUM)
5274 36268 : log_smgrcreate(&dst_rlocator, forkNum);
5275 :
5276 : /* Copy a fork's data, block by block. */
5277 36268 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
5278 : permanent);
5279 : }
5280 : }
5281 109796 : }
5282 :
5283 : /* ---------------------------------------------------------------------
5284 : * FlushDatabaseBuffers
5285 : *
5286 : * This function writes all dirty pages of a database out to disk
5287 : * (or more accurately, out to kernel disk buffers), ensuring that the
5288 : * kernel has an up-to-date view of the database.
5289 : *
5290 : * Generally, the caller should be holding an appropriate lock to ensure
5291 : * no other backend is active in the target database; otherwise more
5292 : * pages could get dirtied.
5293 : *
5294 : * Note we don't worry about flushing any pages of temporary relations.
5295 : * It's assumed these wouldn't be interesting.
5296 : * --------------------------------------------------------------------
5297 : */
5298 : void
5299 8 : FlushDatabaseBuffers(Oid dbid)
5300 : {
5301 : int i;
5302 : BufferDesc *bufHdr;
5303 :
5304 1032 : for (i = 0; i < NBuffers; i++)
5305 : {
5306 : uint32 buf_state;
5307 :
5308 1024 : bufHdr = GetBufferDescriptor(i);
5309 :
5310 : /*
5311 : * As in DropRelationBuffers, an unlocked precheck should be safe and
5312 : * saves some cycles.
5313 : */
5314 1024 : if (bufHdr->tag.dbOid != dbid)
5315 758 : continue;
5316 :
5317 : /* Make sure we can handle the pin */
5318 266 : ReservePrivateRefCountEntry();
5319 266 : ResourceOwnerEnlarge(CurrentResourceOwner);
5320 :
5321 266 : buf_state = LockBufHdr(bufHdr);
5322 266 : if (bufHdr->tag.dbOid == dbid &&
5323 266 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5324 : {
5325 0 : PinBuffer_Locked(bufHdr);
5326 0 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
5327 0 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5328 0 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
5329 0 : UnpinBuffer(bufHdr);
5330 : }
5331 : else
5332 266 : UnlockBufHdr(bufHdr, buf_state);
5333 : }
5334 8 : }
5335 :
5336 : /*
5337 : * Flush a previously, shared or exclusively, locked and pinned buffer to the
5338 : * OS.
5339 : */
5340 : void
5341 158 : FlushOneBuffer(Buffer buffer)
5342 : {
5343 : BufferDesc *bufHdr;
5344 :
5345 : /* currently not needed, but no fundamental reason not to support */
5346 : Assert(!BufferIsLocal(buffer));
5347 :
5348 : Assert(BufferIsPinned(buffer));
5349 :
5350 158 : bufHdr = GetBufferDescriptor(buffer - 1);
5351 :
5352 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
5353 :
5354 158 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5355 158 : }
5356 :
5357 : /*
5358 : * ReleaseBuffer -- release the pin on a buffer
5359 : */
5360 : void
5361 123292936 : ReleaseBuffer(Buffer buffer)
5362 : {
5363 123292936 : if (!BufferIsValid(buffer))
5364 0 : elog(ERROR, "bad buffer ID: %d", buffer);
5365 :
5366 123292936 : if (BufferIsLocal(buffer))
5367 3220036 : UnpinLocalBuffer(buffer);
5368 : else
5369 120072900 : UnpinBuffer(GetBufferDescriptor(buffer - 1));
5370 123292936 : }
5371 :
5372 : /*
5373 : * UnlockReleaseBuffer -- release the content lock and pin on a buffer
5374 : *
5375 : * This is just a shorthand for a common combination.
5376 : */
5377 : void
5378 37759122 : UnlockReleaseBuffer(Buffer buffer)
5379 : {
5380 37759122 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5381 37759122 : ReleaseBuffer(buffer);
5382 37759122 : }
5383 :
5384 : /*
5385 : * IncrBufferRefCount
5386 : * Increment the pin count on a buffer that we have *already* pinned
5387 : * at least once.
5388 : *
5389 : * This function cannot be used on a buffer we do not have pinned,
5390 : * because it doesn't change the shared buffer state.
5391 : */
5392 : void
5393 22830816 : IncrBufferRefCount(Buffer buffer)
5394 : {
5395 : Assert(BufferIsPinned(buffer));
5396 22830816 : ResourceOwnerEnlarge(CurrentResourceOwner);
5397 22830816 : if (BufferIsLocal(buffer))
5398 709124 : LocalRefCount[-buffer - 1]++;
5399 : else
5400 : {
5401 : PrivateRefCountEntry *ref;
5402 :
5403 22121692 : ref = GetPrivateRefCountEntry(buffer, true);
5404 : Assert(ref != NULL);
5405 22121692 : ref->refcount++;
5406 : }
5407 22830816 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
5408 22830816 : }
5409 :
5410 : /*
5411 : * MarkBufferDirtyHint
5412 : *
5413 : * Mark a buffer dirty for non-critical changes.
5414 : *
5415 : * This is essentially the same as MarkBufferDirty, except:
5416 : *
5417 : * 1. The caller does not write WAL; so if checksums are enabled, we may need
5418 : * to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
5419 : * 2. The caller might have only share-lock instead of exclusive-lock on the
5420 : * buffer's content lock.
5421 : * 3. This function does not guarantee that the buffer is always marked dirty
5422 : * (due to a race condition), so it cannot be used for important changes.
5423 : */
5424 : void
5425 19976042 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
5426 : {
5427 : BufferDesc *bufHdr;
5428 19976042 : Page page = BufferGetPage(buffer);
5429 :
5430 19976042 : if (!BufferIsValid(buffer))
5431 0 : elog(ERROR, "bad buffer ID: %d", buffer);
5432 :
5433 19976042 : if (BufferIsLocal(buffer))
5434 : {
5435 1270218 : MarkLocalBufferDirty(buffer);
5436 1270218 : return;
5437 : }
5438 :
5439 18705824 : bufHdr = GetBufferDescriptor(buffer - 1);
5440 :
5441 : Assert(GetPrivateRefCount(buffer) > 0);
5442 : /* here, either share or exclusive lock is OK */
5443 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
5444 :
5445 : /*
5446 : * This routine might get called many times on the same page, if we are
5447 : * making the first scan after commit of an xact that added/deleted many
5448 : * tuples. So, be as quick as we can if the buffer is already dirty. We
5449 : * do this by not acquiring spinlock if it looks like the status bits are
5450 : * already set. Since we make this test unlocked, there's a chance we
5451 : * might fail to notice that the flags have just been cleared, and failed
5452 : * to reset them, due to memory-ordering issues. But since this function
5453 : * is only intended to be used in cases where failing to write out the
5454 : * data would be harmless anyway, it doesn't really matter.
5455 : */
5456 18705824 : if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
5457 : (BM_DIRTY | BM_JUST_DIRTIED))
5458 : {
5459 1883906 : XLogRecPtr lsn = InvalidXLogRecPtr;
5460 1883906 : bool dirtied = false;
5461 1883906 : bool delayChkptFlags = false;
5462 : uint32 buf_state;
5463 :
5464 : /*
5465 : * If we need to protect hint bit updates from torn writes, WAL-log a
5466 : * full page image of the page. This full page image is only necessary
5467 : * if the hint bit update is the first change to the page since the
5468 : * last checkpoint.
5469 : *
5470 : * We don't check full_page_writes here because that logic is included
5471 : * when we call XLogInsert() since the value changes dynamically.
5472 : */
5473 3765622 : if (XLogHintBitIsNeeded() &&
5474 1881716 : (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
5475 : {
5476 : /*
5477 : * If we must not write WAL, due to a relfilelocator-specific
5478 : * condition or being in recovery, don't dirty the page. We can
5479 : * set the hint, just not dirty the page as a result so the hint
5480 : * is lost when we evict the page or shutdown.
5481 : *
5482 : * See src/backend/storage/page/README for longer discussion.
5483 : */
5484 2003584 : if (RecoveryInProgress() ||
5485 121932 : RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
5486 1765406 : return;
5487 :
5488 : /*
5489 : * If the block is already dirty because we either made a change
5490 : * or set a hint already, then we don't need to write a full page
5491 : * image. Note that aggressive cleaning of blocks dirtied by hint
5492 : * bit setting would increase the call rate. Bulk setting of hint
5493 : * bits would reduce the call rate...
5494 : *
5495 : * We must issue the WAL record before we mark the buffer dirty.
5496 : * Otherwise we might write the page before we write the WAL. That
5497 : * causes a race condition, since a checkpoint might occur between
5498 : * writing the WAL record and marking the buffer dirty. We solve
5499 : * that with a kluge, but one that is already in use during
5500 : * transaction commit to prevent race conditions. Basically, we
5501 : * simply prevent the checkpoint WAL record from being written
5502 : * until we have marked the buffer dirty. We don't start the
5503 : * checkpoint flush until we have marked dirty, so our checkpoint
5504 : * must flush the change to disk successfully or the checkpoint
5505 : * never gets written, so crash recovery will fix.
5506 : *
5507 : * It's possible we may enter here without an xid, so it is
5508 : * essential that CreateCheckPoint waits for virtual transactions
5509 : * rather than full transactionids.
5510 : */
5511 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
5512 116246 : MyProc->delayChkptFlags |= DELAY_CHKPT_START;
5513 116246 : delayChkptFlags = true;
5514 116246 : lsn = XLogSaveBufferForHint(buffer, buffer_std);
5515 : }
5516 :
5517 118500 : buf_state = LockBufHdr(bufHdr);
5518 :
5519 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5520 :
5521 118500 : if (!(buf_state & BM_DIRTY))
5522 : {
5523 118442 : dirtied = true; /* Means "will be dirtied by this action" */
5524 :
5525 : /*
5526 : * Set the page LSN if we wrote a backup block. We aren't supposed
5527 : * to set this when only holding a share lock but as long as we
5528 : * serialise it somehow we're OK. We choose to set LSN while
5529 : * holding the buffer header lock, which causes any reader of an
5530 : * LSN who holds only a share lock to also obtain a buffer header
5531 : * lock before using PageGetLSN(), which is enforced in
5532 : * BufferGetLSNAtomic().
5533 : *
5534 : * If checksums are enabled, you might think we should reset the
5535 : * checksum here. That will happen when the page is written
5536 : * sometime later in this checkpoint cycle.
5537 : */
5538 118442 : if (!XLogRecPtrIsInvalid(lsn))
5539 60620 : PageSetLSN(page, lsn);
5540 : }
5541 :
5542 118500 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
5543 118500 : UnlockBufHdr(bufHdr, buf_state);
5544 :
5545 118500 : if (delayChkptFlags)
5546 116246 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
5547 :
5548 118500 : if (dirtied)
5549 : {
5550 118442 : pgBufferUsage.shared_blks_dirtied++;
5551 118442 : if (VacuumCostActive)
5552 2674 : VacuumCostBalance += VacuumCostPageDirty;
5553 : }
5554 : }
5555 : }
5556 :
5557 : /*
5558 : * Release buffer content locks for shared buffers.
5559 : *
5560 : * Used to clean up after errors.
5561 : *
5562 : * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
5563 : * of releasing buffer content locks per se; the only thing we need to deal
5564 : * with here is clearing any PIN_COUNT request that was in progress.
5565 : */
5566 : void
5567 102002 : UnlockBuffers(void)
5568 : {
5569 102002 : BufferDesc *buf = PinCountWaitBuf;
5570 :
5571 102002 : if (buf)
5572 : {
5573 : uint32 buf_state;
5574 :
5575 0 : buf_state = LockBufHdr(buf);
5576 :
5577 : /*
5578 : * Don't complain if flag bit not set; it could have been reset but we
5579 : * got a cancel/die interrupt before getting the signal.
5580 : */
5581 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
5582 0 : buf->wait_backend_pgprocno == MyProcNumber)
5583 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
5584 :
5585 0 : UnlockBufHdr(buf, buf_state);
5586 :
5587 0 : PinCountWaitBuf = NULL;
5588 : }
5589 102002 : }
5590 :
5591 : /*
5592 : * Acquire or release the content_lock for the buffer.
5593 : */
5594 : void
5595 341015038 : LockBuffer(Buffer buffer, int mode)
5596 : {
5597 : BufferDesc *buf;
5598 :
5599 : Assert(BufferIsPinned(buffer));
5600 341015038 : if (BufferIsLocal(buffer))
5601 19799582 : return; /* local buffers need no lock */
5602 :
5603 321215456 : buf = GetBufferDescriptor(buffer - 1);
5604 :
5605 321215456 : if (mode == BUFFER_LOCK_UNLOCK)
5606 162533782 : LWLockRelease(BufferDescriptorGetContentLock(buf));
5607 158681674 : else if (mode == BUFFER_LOCK_SHARE)
5608 112489626 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
5609 46192048 : else if (mode == BUFFER_LOCK_EXCLUSIVE)
5610 46192048 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
5611 : else
5612 0 : elog(ERROR, "unrecognized buffer lock mode: %d", mode);
5613 : }
5614 :
5615 : /*
5616 : * Acquire the content_lock for the buffer, but only if we don't have to wait.
5617 : *
5618 : * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
5619 : */
5620 : bool
5621 3064002 : ConditionalLockBuffer(Buffer buffer)
5622 : {
5623 : BufferDesc *buf;
5624 :
5625 : Assert(BufferIsPinned(buffer));
5626 3064002 : if (BufferIsLocal(buffer))
5627 129502 : return true; /* act as though we got it */
5628 :
5629 2934500 : buf = GetBufferDescriptor(buffer - 1);
5630 :
5631 2934500 : return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
5632 : LW_EXCLUSIVE);
5633 : }
5634 :
5635 : /*
5636 : * Verify that this backend is pinning the buffer exactly once.
5637 : *
5638 : * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
5639 : * holds a pin on the buffer. We do not care whether some other backend does.
5640 : */
5641 : void
5642 4886324 : CheckBufferIsPinnedOnce(Buffer buffer)
5643 : {
5644 4886324 : if (BufferIsLocal(buffer))
5645 : {
5646 1578 : if (LocalRefCount[-buffer - 1] != 1)
5647 0 : elog(ERROR, "incorrect local pin count: %d",
5648 : LocalRefCount[-buffer - 1]);
5649 : }
5650 : else
5651 : {
5652 4884746 : if (GetPrivateRefCount(buffer) != 1)
5653 0 : elog(ERROR, "incorrect local pin count: %d",
5654 : GetPrivateRefCount(buffer));
5655 : }
5656 4886324 : }
5657 :
5658 : /*
5659 : * LockBufferForCleanup - lock a buffer in preparation for deleting items
5660 : *
5661 : * Items may be deleted from a disk page only when the caller (a) holds an
5662 : * exclusive lock on the buffer and (b) has observed that no other backend
5663 : * holds a pin on the buffer. If there is a pin, then the other backend
5664 : * might have a pointer into the buffer (for example, a heapscan reference
5665 : * to an item --- see README for more details). It's OK if a pin is added
5666 : * after the cleanup starts, however; the newly-arrived backend will be
5667 : * unable to look at the page until we release the exclusive lock.
5668 : *
5669 : * To implement this protocol, a would-be deleter must pin the buffer and
5670 : * then call LockBufferForCleanup(). LockBufferForCleanup() is similar to
5671 : * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
5672 : * it has successfully observed pin count = 1.
5673 : */
5674 : void
5675 42270 : LockBufferForCleanup(Buffer buffer)
5676 : {
5677 : BufferDesc *bufHdr;
5678 42270 : TimestampTz waitStart = 0;
5679 42270 : bool waiting = false;
5680 42270 : bool logged_recovery_conflict = false;
5681 :
5682 : Assert(BufferIsPinned(buffer));
5683 : Assert(PinCountWaitBuf == NULL);
5684 :
5685 42270 : CheckBufferIsPinnedOnce(buffer);
5686 :
5687 : /*
5688 : * We do not yet need to be worried about in-progress AIOs holding a pin,
5689 : * as we, so far, only support doing reads via AIO and this function can
5690 : * only be called once the buffer is valid (i.e. no read can be in
5691 : * flight).
5692 : */
5693 :
5694 : /* Nobody else to wait for */
5695 42270 : if (BufferIsLocal(buffer))
5696 32 : return;
5697 :
5698 42238 : bufHdr = GetBufferDescriptor(buffer - 1);
5699 :
5700 : for (;;)
5701 156 : {
5702 : uint32 buf_state;
5703 :
5704 : /* Try to acquire lock */
5705 42394 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
5706 42394 : buf_state = LockBufHdr(bufHdr);
5707 :
5708 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5709 42394 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
5710 : {
5711 : /* Successfully acquired exclusive lock with pincount 1 */
5712 42238 : UnlockBufHdr(bufHdr, buf_state);
5713 :
5714 : /*
5715 : * Emit the log message if recovery conflict on buffer pin was
5716 : * resolved but the startup process waited longer than
5717 : * deadlock_timeout for it.
5718 : */
5719 42238 : if (logged_recovery_conflict)
5720 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
5721 : waitStart, GetCurrentTimestamp(),
5722 : NULL, false);
5723 :
5724 42238 : if (waiting)
5725 : {
5726 : /* reset ps display to remove the suffix if we added one */
5727 4 : set_ps_display_remove_suffix();
5728 4 : waiting = false;
5729 : }
5730 42238 : return;
5731 : }
5732 : /* Failed, so mark myself as waiting for pincount 1 */
5733 156 : if (buf_state & BM_PIN_COUNT_WAITER)
5734 : {
5735 0 : UnlockBufHdr(bufHdr, buf_state);
5736 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5737 0 : elog(ERROR, "multiple backends attempting to wait for pincount 1");
5738 : }
5739 156 : bufHdr->wait_backend_pgprocno = MyProcNumber;
5740 156 : PinCountWaitBuf = bufHdr;
5741 156 : buf_state |= BM_PIN_COUNT_WAITER;
5742 156 : UnlockBufHdr(bufHdr, buf_state);
5743 156 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5744 :
5745 : /* Wait to be signaled by UnpinBuffer() */
5746 156 : if (InHotStandby)
5747 : {
5748 20 : if (!waiting)
5749 : {
5750 : /* adjust the process title to indicate that it's waiting */
5751 4 : set_ps_display_suffix("waiting");
5752 4 : waiting = true;
5753 : }
5754 :
5755 : /*
5756 : * Emit the log message if the startup process is waiting longer
5757 : * than deadlock_timeout for recovery conflict on buffer pin.
5758 : *
5759 : * Skip this if first time through because the startup process has
5760 : * not started waiting yet in this case. So, the wait start
5761 : * timestamp is set after this logic.
5762 : */
5763 20 : if (waitStart != 0 && !logged_recovery_conflict)
5764 : {
5765 8 : TimestampTz now = GetCurrentTimestamp();
5766 :
5767 8 : if (TimestampDifferenceExceeds(waitStart, now,
5768 : DeadlockTimeout))
5769 : {
5770 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
5771 : waitStart, now, NULL, true);
5772 4 : logged_recovery_conflict = true;
5773 : }
5774 : }
5775 :
5776 : /*
5777 : * Set the wait start timestamp if logging is enabled and first
5778 : * time through.
5779 : */
5780 20 : if (log_recovery_conflict_waits && waitStart == 0)
5781 4 : waitStart = GetCurrentTimestamp();
5782 :
5783 : /* Publish the bufid that Startup process waits on */
5784 20 : SetStartupBufferPinWaitBufId(buffer - 1);
5785 : /* Set alarm and then wait to be signaled by UnpinBuffer() */
5786 20 : ResolveRecoveryConflictWithBufferPin();
5787 : /* Reset the published bufid */
5788 20 : SetStartupBufferPinWaitBufId(-1);
5789 : }
5790 : else
5791 136 : ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
5792 :
5793 : /*
5794 : * Remove flag marking us as waiter. Normally this will not be set
5795 : * anymore, but ProcWaitForSignal() can return for other signals as
5796 : * well. We take care to only reset the flag if we're the waiter, as
5797 : * theoretically another backend could have started waiting. That's
5798 : * impossible with the current usages due to table level locking, but
5799 : * better be safe.
5800 : */
5801 156 : buf_state = LockBufHdr(bufHdr);
5802 156 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
5803 16 : bufHdr->wait_backend_pgprocno == MyProcNumber)
5804 16 : buf_state &= ~BM_PIN_COUNT_WAITER;
5805 156 : UnlockBufHdr(bufHdr, buf_state);
5806 :
5807 156 : PinCountWaitBuf = NULL;
5808 : /* Loop back and try again */
5809 : }
5810 : }
5811 :
5812 : /*
5813 : * Check called from ProcessRecoveryConflictInterrupts() when Startup process
5814 : * requests cancellation of all pin holders that are blocking it.
5815 : */
5816 : bool
5817 6 : HoldingBufferPinThatDelaysRecovery(void)
5818 : {
5819 6 : int bufid = GetStartupBufferPinWaitBufId();
5820 :
5821 : /*
5822 : * If we get woken slowly then it's possible that the Startup process was
5823 : * already woken by other backends before we got here. Also possible that
5824 : * we get here by multiple interrupts or interrupts at inappropriate
5825 : * times, so make sure we do nothing if the bufid is not set.
5826 : */
5827 6 : if (bufid < 0)
5828 2 : return false;
5829 :
5830 4 : if (GetPrivateRefCount(bufid + 1) > 0)
5831 4 : return true;
5832 :
5833 0 : return false;
5834 : }
5835 :
5836 : /*
5837 : * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
5838 : *
5839 : * We won't loop, but just check once to see if the pin count is OK. If
5840 : * not, return false with no lock held.
5841 : */
5842 : bool
5843 1156126 : ConditionalLockBufferForCleanup(Buffer buffer)
5844 : {
5845 : BufferDesc *bufHdr;
5846 : uint32 buf_state,
5847 : refcount;
5848 :
5849 : Assert(BufferIsValid(buffer));
5850 :
5851 : /* see AIO related comment in LockBufferForCleanup() */
5852 :
5853 1156126 : if (BufferIsLocal(buffer))
5854 : {
5855 1608 : refcount = LocalRefCount[-buffer - 1];
5856 : /* There should be exactly one pin */
5857 : Assert(refcount > 0);
5858 1608 : if (refcount != 1)
5859 42 : return false;
5860 : /* Nobody else to wait for */
5861 1566 : return true;
5862 : }
5863 :
5864 : /* There should be exactly one local pin */
5865 1154518 : refcount = GetPrivateRefCount(buffer);
5866 : Assert(refcount);
5867 1154518 : if (refcount != 1)
5868 422 : return false;
5869 :
5870 : /* Try to acquire lock */
5871 1154096 : if (!ConditionalLockBuffer(buffer))
5872 84 : return false;
5873 :
5874 1154012 : bufHdr = GetBufferDescriptor(buffer - 1);
5875 1154012 : buf_state = LockBufHdr(bufHdr);
5876 1154012 : refcount = BUF_STATE_GET_REFCOUNT(buf_state);
5877 :
5878 : Assert(refcount > 0);
5879 1154012 : if (refcount == 1)
5880 : {
5881 : /* Successfully acquired exclusive lock with pincount 1 */
5882 1153282 : UnlockBufHdr(bufHdr, buf_state);
5883 1153282 : return true;
5884 : }
5885 :
5886 : /* Failed, so release the lock */
5887 730 : UnlockBufHdr(bufHdr, buf_state);
5888 730 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5889 730 : return false;
5890 : }
5891 :
5892 : /*
5893 : * IsBufferCleanupOK - as above, but we already have the lock
5894 : *
5895 : * Check whether it's OK to perform cleanup on a buffer we've already
5896 : * locked. If we observe that the pin count is 1, our exclusive lock
5897 : * happens to be a cleanup lock, and we can proceed with anything that
5898 : * would have been allowable had we sought a cleanup lock originally.
5899 : */
5900 : bool
5901 4060 : IsBufferCleanupOK(Buffer buffer)
5902 : {
5903 : BufferDesc *bufHdr;
5904 : uint32 buf_state;
5905 :
5906 : Assert(BufferIsValid(buffer));
5907 :
5908 : /* see AIO related comment in LockBufferForCleanup() */
5909 :
5910 4060 : if (BufferIsLocal(buffer))
5911 : {
5912 : /* There should be exactly one pin */
5913 0 : if (LocalRefCount[-buffer - 1] != 1)
5914 0 : return false;
5915 : /* Nobody else to wait for */
5916 0 : return true;
5917 : }
5918 :
5919 : /* There should be exactly one local pin */
5920 4060 : if (GetPrivateRefCount(buffer) != 1)
5921 0 : return false;
5922 :
5923 4060 : bufHdr = GetBufferDescriptor(buffer - 1);
5924 :
5925 : /* caller must hold exclusive lock on buffer */
5926 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
5927 : LW_EXCLUSIVE));
5928 :
5929 4060 : buf_state = LockBufHdr(bufHdr);
5930 :
5931 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5932 4060 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
5933 : {
5934 : /* pincount is OK. */
5935 4060 : UnlockBufHdr(bufHdr, buf_state);
5936 4060 : return true;
5937 : }
5938 :
5939 0 : UnlockBufHdr(bufHdr, buf_state);
5940 0 : return false;
5941 : }
5942 :
5943 :
5944 : /*
5945 : * Functions for buffer I/O handling
5946 : *
5947 : * Also note that these are used only for shared buffers, not local ones.
5948 : */
5949 :
5950 : /*
5951 : * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
5952 : */
5953 : static void
5954 14944 : WaitIO(BufferDesc *buf)
5955 : {
5956 14944 : ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
5957 :
5958 14944 : ConditionVariablePrepareToSleep(cv);
5959 : for (;;)
5960 14850 : {
5961 : uint32 buf_state;
5962 : PgAioWaitRef iow;
5963 :
5964 : /*
5965 : * It may not be necessary to acquire the spinlock to check the flag
5966 : * here, but since this test is essential for correctness, we'd better
5967 : * play it safe.
5968 : */
5969 29794 : buf_state = LockBufHdr(buf);
5970 :
5971 : /*
5972 : * Copy the wait reference while holding the spinlock. This protects
5973 : * against a concurrent TerminateBufferIO() in another backend from
5974 : * clearing the wref while it's being read.
5975 : */
5976 29794 : iow = buf->io_wref;
5977 29794 : UnlockBufHdr(buf, buf_state);
5978 :
5979 : /* no IO in progress, we don't need to wait */
5980 29794 : if (!(buf_state & BM_IO_IN_PROGRESS))
5981 14944 : break;
5982 :
5983 : /*
5984 : * The buffer has asynchronous IO in progress, wait for it to
5985 : * complete.
5986 : */
5987 14850 : if (pgaio_wref_valid(&iow))
5988 : {
5989 12418 : pgaio_wref_wait(&iow);
5990 :
5991 : /*
5992 : * The AIO subsystem internally uses condition variables and thus
5993 : * might remove this backend from the BufferDesc's CV. While that
5994 : * wouldn't cause a correctness issue (the first CV sleep just
5995 : * immediately returns if not already registered), it seems worth
5996 : * avoiding unnecessary loop iterations, given that we take care
5997 : * to do so at the start of the function.
5998 : */
5999 12418 : ConditionVariablePrepareToSleep(cv);
6000 12418 : continue;
6001 : }
6002 :
6003 : /* wait on BufferDesc->cv, e.g. for concurrent synchronous IO */
6004 2432 : ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
6005 : }
6006 14944 : ConditionVariableCancelSleep();
6007 14944 : }
6008 :
6009 : /*
6010 : * StartBufferIO: begin I/O on this buffer
6011 : * (Assumptions)
6012 : * My process is executing no IO on this buffer
6013 : * The buffer is Pinned
6014 : *
6015 : * In some scenarios multiple backends could attempt the same I/O operation
6016 : * concurrently. If someone else has already started I/O on this buffer then
6017 : * we will wait for completion of the IO using WaitIO().
6018 : *
6019 : * Input operations are only attempted on buffers that are not BM_VALID,
6020 : * and output operations only on buffers that are BM_VALID and BM_DIRTY,
6021 : * so we can always tell if the work is already done.
6022 : *
6023 : * Returns true if we successfully marked the buffer as I/O busy,
6024 : * false if someone else already did the work.
6025 : *
6026 : * If nowait is true, then we don't wait for an I/O to be finished by another
6027 : * backend. In that case, false indicates either that the I/O was already
6028 : * finished, or is still in progress. This is useful for callers that want to
6029 : * find out if they can perform the I/O as part of a larger operation, without
6030 : * waiting for the answer or distinguishing the reasons why not.
6031 : */
6032 : bool
6033 4872780 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
6034 : {
6035 : uint32 buf_state;
6036 :
6037 4872780 : ResourceOwnerEnlarge(CurrentResourceOwner);
6038 :
6039 : for (;;)
6040 : {
6041 4887712 : buf_state = LockBufHdr(buf);
6042 :
6043 4887712 : if (!(buf_state & BM_IO_IN_PROGRESS))
6044 4872772 : break;
6045 14940 : UnlockBufHdr(buf, buf_state);
6046 14940 : if (nowait)
6047 8 : return false;
6048 14932 : WaitIO(buf);
6049 : }
6050 :
6051 : /* Once we get here, there is definitely no I/O active on this buffer */
6052 :
6053 : /* Check if someone else already did the I/O */
6054 4872772 : if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
6055 : {
6056 15722 : UnlockBufHdr(buf, buf_state);
6057 15722 : return false;
6058 : }
6059 :
6060 4857050 : buf_state |= BM_IO_IN_PROGRESS;
6061 4857050 : UnlockBufHdr(buf, buf_state);
6062 :
6063 4857050 : ResourceOwnerRememberBufferIO(CurrentResourceOwner,
6064 : BufferDescriptorGetBuffer(buf));
6065 :
6066 4857050 : return true;
6067 : }
6068 :
6069 : /*
6070 : * TerminateBufferIO: release a buffer we were doing I/O on
6071 : * (Assumptions)
6072 : * My process is executing IO for the buffer
6073 : * BM_IO_IN_PROGRESS bit is set for the buffer
6074 : * The buffer is Pinned
6075 : *
6076 : * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
6077 : * buffer's BM_DIRTY flag. This is appropriate when terminating a
6078 : * successful write. The check on BM_JUST_DIRTIED is necessary to avoid
6079 : * marking the buffer clean if it was re-dirtied while we were writing.
6080 : *
6081 : * set_flag_bits gets ORed into the buffer's flags. It must include
6082 : * BM_IO_ERROR in a failure case. For successful completion it could
6083 : * be 0, or BM_VALID if we just finished reading in the page.
6084 : *
6085 : * If forget_owner is true, we release the buffer I/O from the current
6086 : * resource owner. (forget_owner=false is used when the resource owner itself
6087 : * is being released)
6088 : */
6089 : void
6090 4582124 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits,
6091 : bool forget_owner, bool release_aio)
6092 : {
6093 : uint32 buf_state;
6094 :
6095 4582124 : buf_state = LockBufHdr(buf);
6096 :
6097 : Assert(buf_state & BM_IO_IN_PROGRESS);
6098 4582124 : buf_state &= ~BM_IO_IN_PROGRESS;
6099 :
6100 : /* Clear earlier errors, if this IO failed, it'll be marked again */
6101 4582124 : buf_state &= ~BM_IO_ERROR;
6102 :
6103 4582124 : if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
6104 1098920 : buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
6105 :
6106 4582124 : if (release_aio)
6107 : {
6108 : /* release ownership by the AIO subsystem */
6109 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
6110 2490276 : buf_state -= BUF_REFCOUNT_ONE;
6111 2490276 : pgaio_wref_clear(&buf->io_wref);
6112 : }
6113 :
6114 4582124 : buf_state |= set_flag_bits;
6115 4582124 : UnlockBufHdr(buf, buf_state);
6116 :
6117 4582124 : if (forget_owner)
6118 2091806 : ResourceOwnerForgetBufferIO(CurrentResourceOwner,
6119 : BufferDescriptorGetBuffer(buf));
6120 :
6121 4582124 : ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
6122 :
6123 : /*
6124 : * Support LockBufferForCleanup()
6125 : *
6126 : * We may have just released the last pin other than the waiter's. In most
6127 : * cases, this backend holds another pin on the buffer. But, if, for
6128 : * example, this backend is completing an IO issued by another backend, it
6129 : * may be time to wake the waiter.
6130 : */
6131 4582124 : if (release_aio && (buf_state & BM_PIN_COUNT_WAITER))
6132 0 : WakePinCountWaiter(buf);
6133 4582124 : }
6134 :
6135 : /*
6136 : * AbortBufferIO: Clean up active buffer I/O after an error.
6137 : *
6138 : * All LWLocks we might have held have been released,
6139 : * but we haven't yet released buffer pins, so the buffer is still pinned.
6140 : *
6141 : * If I/O was in progress, we always set BM_IO_ERROR, even though it's
6142 : * possible the error condition wasn't related to the I/O.
6143 : *
6144 : * Note: this does not remove the buffer I/O from the resource owner.
6145 : * That's correct when we're releasing the whole resource owner, but
6146 : * beware if you use this in other contexts.
6147 : */
6148 : static void
6149 30 : AbortBufferIO(Buffer buffer)
6150 : {
6151 30 : BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
6152 : uint32 buf_state;
6153 :
6154 30 : buf_state = LockBufHdr(buf_hdr);
6155 : Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
6156 :
6157 30 : if (!(buf_state & BM_VALID))
6158 : {
6159 : Assert(!(buf_state & BM_DIRTY));
6160 30 : UnlockBufHdr(buf_hdr, buf_state);
6161 : }
6162 : else
6163 : {
6164 : Assert(buf_state & BM_DIRTY);
6165 0 : UnlockBufHdr(buf_hdr, buf_state);
6166 :
6167 : /* Issue notice if this is not the first failure... */
6168 0 : if (buf_state & BM_IO_ERROR)
6169 : {
6170 : /* Buffer is pinned, so we can read tag without spinlock */
6171 0 : ereport(WARNING,
6172 : (errcode(ERRCODE_IO_ERROR),
6173 : errmsg("could not write block %u of %s",
6174 : buf_hdr->tag.blockNum,
6175 : relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
6176 : BufTagGetForkNum(&buf_hdr->tag)).str),
6177 : errdetail("Multiple failures --- write error might be permanent.")));
6178 : }
6179 : }
6180 :
6181 30 : TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false, false);
6182 30 : }
6183 :
6184 : /*
6185 : * Error context callback for errors occurring during shared buffer writes.
6186 : */
6187 : static void
6188 70 : shared_buffer_write_error_callback(void *arg)
6189 : {
6190 70 : BufferDesc *bufHdr = (BufferDesc *) arg;
6191 :
6192 : /* Buffer is pinned, so we can read the tag without locking the spinlock */
6193 70 : if (bufHdr != NULL)
6194 140 : errcontext("writing block %u of relation %s",
6195 : bufHdr->tag.blockNum,
6196 70 : relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
6197 : BufTagGetForkNum(&bufHdr->tag)).str);
6198 70 : }
6199 :
6200 : /*
6201 : * Error context callback for errors occurring during local buffer writes.
6202 : */
6203 : static void
6204 0 : local_buffer_write_error_callback(void *arg)
6205 : {
6206 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
6207 :
6208 0 : if (bufHdr != NULL)
6209 0 : errcontext("writing block %u of relation %s",
6210 : bufHdr->tag.blockNum,
6211 0 : relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
6212 : MyProcNumber,
6213 : BufTagGetForkNum(&bufHdr->tag)).str);
6214 0 : }
6215 :
6216 : /*
6217 : * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
6218 : */
6219 : static int
6220 18430480 : rlocator_comparator(const void *p1, const void *p2)
6221 : {
6222 18430480 : RelFileLocator n1 = *(const RelFileLocator *) p1;
6223 18430480 : RelFileLocator n2 = *(const RelFileLocator *) p2;
6224 :
6225 18430480 : if (n1.relNumber < n2.relNumber)
6226 18354716 : return -1;
6227 75764 : else if (n1.relNumber > n2.relNumber)
6228 72332 : return 1;
6229 :
6230 3432 : if (n1.dbOid < n2.dbOid)
6231 0 : return -1;
6232 3432 : else if (n1.dbOid > n2.dbOid)
6233 0 : return 1;
6234 :
6235 3432 : if (n1.spcOid < n2.spcOid)
6236 0 : return -1;
6237 3432 : else if (n1.spcOid > n2.spcOid)
6238 0 : return 1;
6239 : else
6240 3432 : return 0;
6241 : }
6242 :
6243 : /*
6244 : * Lock buffer header - set BM_LOCKED in buffer state.
6245 : */
6246 : uint32
6247 72108670 : LockBufHdr(BufferDesc *desc)
6248 : {
6249 : SpinDelayStatus delayStatus;
6250 : uint32 old_buf_state;
6251 :
6252 : Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
6253 :
6254 72108670 : init_local_spin_delay(&delayStatus);
6255 :
6256 : while (true)
6257 : {
6258 : /* set BM_LOCKED flag */
6259 72132544 : old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
6260 : /* if it wasn't set before we're OK */
6261 72132544 : if (!(old_buf_state & BM_LOCKED))
6262 72108670 : break;
6263 23874 : perform_spin_delay(&delayStatus);
6264 : }
6265 72108670 : finish_spin_delay(&delayStatus);
6266 72108670 : return old_buf_state | BM_LOCKED;
6267 : }
6268 :
6269 : /*
6270 : * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
6271 : * state at that point.
6272 : *
6273 : * Obviously the buffer could be locked by the time the value is returned, so
6274 : * this is primarily useful in CAS style loops.
6275 : */
6276 : static uint32
6277 3626 : WaitBufHdrUnlocked(BufferDesc *buf)
6278 : {
6279 : SpinDelayStatus delayStatus;
6280 : uint32 buf_state;
6281 :
6282 3626 : init_local_spin_delay(&delayStatus);
6283 :
6284 3626 : buf_state = pg_atomic_read_u32(&buf->state);
6285 :
6286 10356 : while (buf_state & BM_LOCKED)
6287 : {
6288 6730 : perform_spin_delay(&delayStatus);
6289 6730 : buf_state = pg_atomic_read_u32(&buf->state);
6290 : }
6291 :
6292 3626 : finish_spin_delay(&delayStatus);
6293 :
6294 3626 : return buf_state;
6295 : }
6296 :
6297 : /*
6298 : * BufferTag comparator.
6299 : */
6300 : static inline int
6301 0 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
6302 : {
6303 : int ret;
6304 : RelFileLocator rlocatora;
6305 : RelFileLocator rlocatorb;
6306 :
6307 0 : rlocatora = BufTagGetRelFileLocator(ba);
6308 0 : rlocatorb = BufTagGetRelFileLocator(bb);
6309 :
6310 0 : ret = rlocator_comparator(&rlocatora, &rlocatorb);
6311 :
6312 0 : if (ret != 0)
6313 0 : return ret;
6314 :
6315 0 : if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
6316 0 : return -1;
6317 0 : if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
6318 0 : return 1;
6319 :
6320 0 : if (ba->blockNum < bb->blockNum)
6321 0 : return -1;
6322 0 : if (ba->blockNum > bb->blockNum)
6323 0 : return 1;
6324 :
6325 0 : return 0;
6326 : }
6327 :
6328 : /*
6329 : * Comparator determining the writeout order in a checkpoint.
6330 : *
6331 : * It is important that tablespaces are compared first, the logic balancing
6332 : * writes between tablespaces relies on it.
6333 : */
6334 : static inline int
6335 5949948 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
6336 : {
6337 : /* compare tablespace */
6338 5949948 : if (a->tsId < b->tsId)
6339 15074 : return -1;
6340 5934874 : else if (a->tsId > b->tsId)
6341 51244 : return 1;
6342 : /* compare relation */
6343 5883630 : if (a->relNumber < b->relNumber)
6344 1654780 : return -1;
6345 4228850 : else if (a->relNumber > b->relNumber)
6346 1576758 : return 1;
6347 : /* compare fork */
6348 2652092 : else if (a->forkNum < b->forkNum)
6349 109882 : return -1;
6350 2542210 : else if (a->forkNum > b->forkNum)
6351 118982 : return 1;
6352 : /* compare block number */
6353 2423228 : else if (a->blockNum < b->blockNum)
6354 1193626 : return -1;
6355 1229602 : else if (a->blockNum > b->blockNum)
6356 1157404 : return 1;
6357 : /* equal page IDs are unlikely, but not impossible */
6358 72198 : return 0;
6359 : }
6360 :
6361 : /*
6362 : * Comparator for a Min-Heap over the per-tablespace checkpoint completion
6363 : * progress.
6364 : */
6365 : static int
6366 483782 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
6367 : {
6368 483782 : CkptTsStatus *sa = (CkptTsStatus *) DatumGetPointer(a);
6369 483782 : CkptTsStatus *sb = (CkptTsStatus *) DatumGetPointer(b);
6370 :
6371 : /* we want a min-heap, so return 1 for the a < b */
6372 483782 : if (sa->progress < sb->progress)
6373 433302 : return 1;
6374 50480 : else if (sa->progress == sb->progress)
6375 2066 : return 0;
6376 : else
6377 48414 : return -1;
6378 : }
6379 :
6380 : /*
6381 : * Initialize a writeback context, discarding potential previous state.
6382 : *
6383 : * *max_pending is a pointer instead of an immediate value, so the coalesce
6384 : * limits can easily changed by the GUC mechanism, and so calling code does
6385 : * not have to check the current configuration. A value of 0 means that no
6386 : * writeback control will be performed.
6387 : */
6388 : void
6389 5242 : WritebackContextInit(WritebackContext *context, int *max_pending)
6390 : {
6391 : Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
6392 :
6393 5242 : context->max_pending = max_pending;
6394 5242 : context->nr_pending = 0;
6395 5242 : }
6396 :
6397 : /*
6398 : * Add buffer to list of pending writeback requests.
6399 : */
6400 : void
6401 1088612 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
6402 : BufferTag *tag)
6403 : {
6404 : PendingWriteback *pending;
6405 :
6406 : /*
6407 : * As pg_flush_data() doesn't do anything with fsync disabled, there's no
6408 : * point in tracking in that case.
6409 : */
6410 1088612 : if (io_direct_flags & IO_DIRECT_DATA ||
6411 1087536 : !enableFsync)
6412 1088612 : return;
6413 :
6414 : /*
6415 : * Add buffer to the pending writeback array, unless writeback control is
6416 : * disabled.
6417 : */
6418 0 : if (*wb_context->max_pending > 0)
6419 : {
6420 : Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
6421 :
6422 0 : pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
6423 :
6424 0 : pending->tag = *tag;
6425 : }
6426 :
6427 : /*
6428 : * Perform pending flushes if the writeback limit is exceeded. This
6429 : * includes the case where previously an item has been added, but control
6430 : * is now disabled.
6431 : */
6432 0 : if (wb_context->nr_pending >= *wb_context->max_pending)
6433 0 : IssuePendingWritebacks(wb_context, io_context);
6434 : }
6435 :
6436 : #define ST_SORT sort_pending_writebacks
6437 : #define ST_ELEMENT_TYPE PendingWriteback
6438 : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
6439 : #define ST_SCOPE static
6440 : #define ST_DEFINE
6441 : #include "lib/sort_template.h"
6442 :
6443 : /*
6444 : * Issue all pending writeback requests, previously scheduled with
6445 : * ScheduleBufferTagForWriteback, to the OS.
6446 : *
6447 : * Because this is only used to improve the OSs IO scheduling we try to never
6448 : * error out - it's just a hint.
6449 : */
6450 : void
6451 2076 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
6452 : {
6453 : instr_time io_start;
6454 : int i;
6455 :
6456 2076 : if (wb_context->nr_pending == 0)
6457 2076 : return;
6458 :
6459 : /*
6460 : * Executing the writes in-order can make them a lot faster, and allows to
6461 : * merge writeback requests to consecutive blocks into larger writebacks.
6462 : */
6463 0 : sort_pending_writebacks(wb_context->pending_writebacks,
6464 0 : wb_context->nr_pending);
6465 :
6466 0 : io_start = pgstat_prepare_io_time(track_io_timing);
6467 :
6468 : /*
6469 : * Coalesce neighbouring writes, but nothing else. For that we iterate
6470 : * through the, now sorted, array of pending flushes, and look forward to
6471 : * find all neighbouring (or identical) writes.
6472 : */
6473 0 : for (i = 0; i < wb_context->nr_pending; i++)
6474 : {
6475 : PendingWriteback *cur;
6476 : PendingWriteback *next;
6477 : SMgrRelation reln;
6478 : int ahead;
6479 : BufferTag tag;
6480 : RelFileLocator currlocator;
6481 0 : Size nblocks = 1;
6482 :
6483 0 : cur = &wb_context->pending_writebacks[i];
6484 0 : tag = cur->tag;
6485 0 : currlocator = BufTagGetRelFileLocator(&tag);
6486 :
6487 : /*
6488 : * Peek ahead, into following writeback requests, to see if they can
6489 : * be combined with the current one.
6490 : */
6491 0 : for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
6492 : {
6493 :
6494 0 : next = &wb_context->pending_writebacks[i + ahead + 1];
6495 :
6496 : /* different file, stop */
6497 0 : if (!RelFileLocatorEquals(currlocator,
6498 0 : BufTagGetRelFileLocator(&next->tag)) ||
6499 0 : BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
6500 : break;
6501 :
6502 : /* ok, block queued twice, skip */
6503 0 : if (cur->tag.blockNum == next->tag.blockNum)
6504 0 : continue;
6505 :
6506 : /* only merge consecutive writes */
6507 0 : if (cur->tag.blockNum + 1 != next->tag.blockNum)
6508 0 : break;
6509 :
6510 0 : nblocks++;
6511 0 : cur = next;
6512 : }
6513 :
6514 0 : i += ahead;
6515 :
6516 : /* and finally tell the kernel to write the data to storage */
6517 0 : reln = smgropen(currlocator, INVALID_PROC_NUMBER);
6518 0 : smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
6519 : }
6520 :
6521 : /*
6522 : * Assume that writeback requests are only issued for buffers containing
6523 : * blocks of permanent relations.
6524 : */
6525 0 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
6526 0 : IOOP_WRITEBACK, io_start, wb_context->nr_pending, 0);
6527 :
6528 0 : wb_context->nr_pending = 0;
6529 : }
6530 :
6531 : /* ResourceOwner callbacks */
6532 :
6533 : static void
6534 30 : ResOwnerReleaseBufferIO(Datum res)
6535 : {
6536 30 : Buffer buffer = DatumGetInt32(res);
6537 :
6538 30 : AbortBufferIO(buffer);
6539 30 : }
6540 :
6541 : static char *
6542 0 : ResOwnerPrintBufferIO(Datum res)
6543 : {
6544 0 : Buffer buffer = DatumGetInt32(res);
6545 :
6546 0 : return psprintf("lost track of buffer IO on buffer %d", buffer);
6547 : }
6548 :
6549 : static void
6550 14782 : ResOwnerReleaseBufferPin(Datum res)
6551 : {
6552 14782 : Buffer buffer = DatumGetInt32(res);
6553 :
6554 : /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
6555 14782 : if (!BufferIsValid(buffer))
6556 0 : elog(ERROR, "bad buffer ID: %d", buffer);
6557 :
6558 14782 : if (BufferIsLocal(buffer))
6559 5970 : UnpinLocalBufferNoOwner(buffer);
6560 : else
6561 8812 : UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
6562 14782 : }
6563 :
6564 : static char *
6565 0 : ResOwnerPrintBufferPin(Datum res)
6566 : {
6567 0 : return DebugPrintBufferRefcount(DatumGetInt32(res));
6568 : }
6569 :
6570 : /*
6571 : * Helper function to evict unpinned buffer whose buffer header lock is
6572 : * already acquired.
6573 : */
6574 : static bool
6575 4270 : EvictUnpinnedBufferInternal(BufferDesc *desc, bool *buffer_flushed)
6576 : {
6577 : uint32 buf_state;
6578 : bool result;
6579 :
6580 4270 : *buffer_flushed = false;
6581 :
6582 4270 : buf_state = pg_atomic_read_u32(&(desc->state));
6583 : Assert(buf_state & BM_LOCKED);
6584 :
6585 4270 : if ((buf_state & BM_VALID) == 0)
6586 : {
6587 0 : UnlockBufHdr(desc, buf_state);
6588 0 : return false;
6589 : }
6590 :
6591 : /* Check that it's not pinned already. */
6592 4270 : if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
6593 : {
6594 0 : UnlockBufHdr(desc, buf_state);
6595 0 : return false;
6596 : }
6597 :
6598 4270 : PinBuffer_Locked(desc); /* releases spinlock */
6599 :
6600 : /* If it was dirty, try to clean it once. */
6601 4270 : if (buf_state & BM_DIRTY)
6602 : {
6603 1936 : LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED);
6604 1936 : FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
6605 1936 : *buffer_flushed = true;
6606 1936 : LWLockRelease(BufferDescriptorGetContentLock(desc));
6607 : }
6608 :
6609 : /* This will return false if it becomes dirty or someone else pins it. */
6610 4270 : result = InvalidateVictimBuffer(desc);
6611 :
6612 4270 : UnpinBuffer(desc);
6613 :
6614 4270 : return result;
6615 : }
6616 :
6617 : /*
6618 : * Try to evict the current block in a shared buffer.
6619 : *
6620 : * This function is intended for testing/development use only!
6621 : *
6622 : * To succeed, the buffer must not be pinned on entry, so if the caller had a
6623 : * particular block in mind, it might already have been replaced by some other
6624 : * block by the time this function runs. It's also unpinned on return, so the
6625 : * buffer might be occupied again by the time control is returned, potentially
6626 : * even by the same block. This inherent raciness without other interlocking
6627 : * makes the function unsuitable for non-testing usage.
6628 : *
6629 : * *buffer_flushed is set to true if the buffer was dirty and has been
6630 : * flushed, false otherwise. However, *buffer_flushed=true does not
6631 : * necessarily mean that we flushed the buffer, it could have been flushed by
6632 : * someone else.
6633 : *
6634 : * Returns true if the buffer was valid and it has now been made invalid.
6635 : * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
6636 : * or if the buffer becomes dirty again while we're trying to write it out.
6637 : */
6638 : bool
6639 280 : EvictUnpinnedBuffer(Buffer buf, bool *buffer_flushed)
6640 : {
6641 : BufferDesc *desc;
6642 :
6643 : Assert(BufferIsValid(buf) && !BufferIsLocal(buf));
6644 :
6645 : /* Make sure we can pin the buffer. */
6646 280 : ResourceOwnerEnlarge(CurrentResourceOwner);
6647 280 : ReservePrivateRefCountEntry();
6648 :
6649 280 : desc = GetBufferDescriptor(buf - 1);
6650 280 : LockBufHdr(desc);
6651 :
6652 280 : return EvictUnpinnedBufferInternal(desc, buffer_flushed);
6653 : }
6654 :
6655 : /*
6656 : * Try to evict all the shared buffers.
6657 : *
6658 : * This function is intended for testing/development use only! See
6659 : * EvictUnpinnedBuffer().
6660 : *
6661 : * The buffers_* parameters are mandatory and indicate the total count of
6662 : * buffers that:
6663 : * - buffers_evicted - were evicted
6664 : * - buffers_flushed - were flushed
6665 : * - buffers_skipped - could not be evicted
6666 : */
6667 : void
6668 2 : EvictAllUnpinnedBuffers(int32 *buffers_evicted, int32 *buffers_flushed,
6669 : int32 *buffers_skipped)
6670 : {
6671 2 : *buffers_evicted = 0;
6672 2 : *buffers_skipped = 0;
6673 2 : *buffers_flushed = 0;
6674 :
6675 32770 : for (int buf = 1; buf <= NBuffers; buf++)
6676 : {
6677 32768 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
6678 : uint32 buf_state;
6679 : bool buffer_flushed;
6680 :
6681 32768 : buf_state = pg_atomic_read_u32(&desc->state);
6682 32768 : if (!(buf_state & BM_VALID))
6683 28778 : continue;
6684 :
6685 3990 : ResourceOwnerEnlarge(CurrentResourceOwner);
6686 3990 : ReservePrivateRefCountEntry();
6687 :
6688 3990 : LockBufHdr(desc);
6689 :
6690 3990 : if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
6691 3990 : (*buffers_evicted)++;
6692 : else
6693 0 : (*buffers_skipped)++;
6694 :
6695 3990 : if (buffer_flushed)
6696 1898 : (*buffers_flushed)++;
6697 : }
6698 2 : }
6699 :
6700 : /*
6701 : * Try to evict all the shared buffers containing provided relation's pages.
6702 : *
6703 : * This function is intended for testing/development use only! See
6704 : * EvictUnpinnedBuffer().
6705 : *
6706 : * The caller must hold at least AccessShareLock on the relation to prevent
6707 : * the relation from being dropped.
6708 : *
6709 : * The buffers_* parameters are mandatory and indicate the total count of
6710 : * buffers that:
6711 : * - buffers_evicted - were evicted
6712 : * - buffers_flushed - were flushed
6713 : * - buffers_skipped - could not be evicted
6714 : */
6715 : void
6716 2 : EvictRelUnpinnedBuffers(Relation rel, int32 *buffers_evicted,
6717 : int32 *buffers_flushed, int32 *buffers_skipped)
6718 : {
6719 : Assert(!RelationUsesLocalBuffers(rel));
6720 :
6721 2 : *buffers_skipped = 0;
6722 2 : *buffers_evicted = 0;
6723 2 : *buffers_flushed = 0;
6724 :
6725 32770 : for (int buf = 1; buf <= NBuffers; buf++)
6726 : {
6727 32768 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
6728 32768 : uint32 buf_state = pg_atomic_read_u32(&(desc->state));
6729 : bool buffer_flushed;
6730 :
6731 : /* An unlocked precheck should be safe and saves some cycles. */
6732 32768 : if ((buf_state & BM_VALID) == 0 ||
6733 56 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
6734 32768 : continue;
6735 :
6736 : /* Make sure we can pin the buffer. */
6737 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
6738 0 : ReservePrivateRefCountEntry();
6739 :
6740 0 : buf_state = LockBufHdr(desc);
6741 :
6742 : /* recheck, could have changed without the lock */
6743 0 : if ((buf_state & BM_VALID) == 0 ||
6744 0 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
6745 : {
6746 0 : UnlockBufHdr(desc, buf_state);
6747 0 : continue;
6748 : }
6749 :
6750 0 : if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
6751 0 : (*buffers_evicted)++;
6752 : else
6753 0 : (*buffers_skipped)++;
6754 :
6755 0 : if (buffer_flushed)
6756 0 : (*buffers_flushed)++;
6757 : }
6758 2 : }
6759 :
6760 : /*
6761 : * Generic implementation of the AIO handle staging callback for readv/writev
6762 : * on local/shared buffers.
6763 : *
6764 : * Each readv/writev can target multiple buffers. The buffers have already
6765 : * been registered with the IO handle.
6766 : *
6767 : * To make the IO ready for execution ("staging"), we need to ensure that the
6768 : * targeted buffers are in an appropriate state while the IO is ongoing. For
6769 : * that the AIO subsystem needs to have its own buffer pin, otherwise an error
6770 : * in this backend could lead to this backend's buffer pin being released as
6771 : * part of error handling, which in turn could lead to the buffer being
6772 : * replaced while IO is ongoing.
6773 : */
6774 : static pg_attribute_always_inline void
6775 2455316 : buffer_stage_common(PgAioHandle *ioh, bool is_write, bool is_temp)
6776 : {
6777 : uint64 *io_data;
6778 : uint8 handle_data_len;
6779 : PgAioWaitRef io_ref;
6780 2455316 : BufferTag first PG_USED_FOR_ASSERTS_ONLY = {0};
6781 :
6782 2455316 : io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
6783 :
6784 2455316 : pgaio_io_get_wref(ioh, &io_ref);
6785 :
6786 : /* iterate over all buffers affected by the vectored readv/writev */
6787 5237324 : for (int i = 0; i < handle_data_len; i++)
6788 : {
6789 2782008 : Buffer buffer = (Buffer) io_data[i];
6790 2782008 : BufferDesc *buf_hdr = is_temp ?
6791 16806 : GetLocalBufferDescriptor(-buffer - 1)
6792 2782008 : : GetBufferDescriptor(buffer - 1);
6793 : uint32 buf_state;
6794 :
6795 : /*
6796 : * Check that all the buffers are actually ones that could conceivably
6797 : * be done in one IO, i.e. are sequential. This is the last
6798 : * buffer-aware code before IO is actually executed and confusion
6799 : * about which buffers are targeted by IO can be hard to debug, making
6800 : * it worth doing extra-paranoid checks.
6801 : */
6802 2782008 : if (i == 0)
6803 2455316 : first = buf_hdr->tag;
6804 : else
6805 : {
6806 : Assert(buf_hdr->tag.relNumber == first.relNumber);
6807 : Assert(buf_hdr->tag.blockNum == first.blockNum + i);
6808 : }
6809 :
6810 2782008 : if (is_temp)
6811 16806 : buf_state = pg_atomic_read_u32(&buf_hdr->state);
6812 : else
6813 2765202 : buf_state = LockBufHdr(buf_hdr);
6814 :
6815 : /* verify the buffer is in the expected state */
6816 : Assert(buf_state & BM_TAG_VALID);
6817 : if (is_write)
6818 : {
6819 : Assert(buf_state & BM_VALID);
6820 : Assert(buf_state & BM_DIRTY);
6821 : }
6822 : else
6823 : {
6824 : Assert(!(buf_state & BM_VALID));
6825 : Assert(!(buf_state & BM_DIRTY));
6826 : }
6827 :
6828 : /* temp buffers don't use BM_IO_IN_PROGRESS */
6829 2782008 : if (!is_temp)
6830 : Assert(buf_state & BM_IO_IN_PROGRESS);
6831 :
6832 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) >= 1);
6833 :
6834 : /*
6835 : * Reflect that the buffer is now owned by the AIO subsystem.
6836 : *
6837 : * For local buffers: This can't be done just via LocalRefCount, as
6838 : * one might initially think, as this backend could error out while
6839 : * AIO is still in progress, releasing all the pins by the backend
6840 : * itself.
6841 : *
6842 : * This pin is released again in TerminateBufferIO().
6843 : */
6844 2782008 : buf_state += BUF_REFCOUNT_ONE;
6845 2782008 : buf_hdr->io_wref = io_ref;
6846 :
6847 2782008 : if (is_temp)
6848 16806 : pg_atomic_unlocked_write_u32(&buf_hdr->state, buf_state);
6849 : else
6850 2765202 : UnlockBufHdr(buf_hdr, buf_state);
6851 :
6852 : /*
6853 : * Ensure the content lock that prevents buffer modifications while
6854 : * the buffer is being written out is not released early due to an
6855 : * error.
6856 : */
6857 2782008 : if (is_write && !is_temp)
6858 : {
6859 : LWLock *content_lock;
6860 :
6861 0 : content_lock = BufferDescriptorGetContentLock(buf_hdr);
6862 :
6863 : Assert(LWLockHeldByMe(content_lock));
6864 :
6865 : /*
6866 : * Lock is now owned by AIO subsystem.
6867 : */
6868 0 : LWLockDisown(content_lock);
6869 : }
6870 :
6871 : /*
6872 : * Stop tracking this buffer via the resowner - the AIO system now
6873 : * keeps track.
6874 : */
6875 2782008 : if (!is_temp)
6876 2765202 : ResourceOwnerForgetBufferIO(CurrentResourceOwner, buffer);
6877 : }
6878 2455316 : }
6879 :
6880 : /*
6881 : * Decode readv errors as encoded by buffer_readv_encode_error().
6882 : */
6883 : static inline void
6884 698 : buffer_readv_decode_error(PgAioResult result,
6885 : bool *zeroed_any,
6886 : bool *ignored_any,
6887 : uint8 *zeroed_or_error_count,
6888 : uint8 *checkfail_count,
6889 : uint8 *first_off)
6890 : {
6891 698 : uint32 rem_error = result.error_data;
6892 :
6893 : /* see static asserts in buffer_readv_encode_error */
6894 : #define READV_COUNT_BITS 7
6895 : #define READV_COUNT_MASK ((1 << READV_COUNT_BITS) - 1)
6896 :
6897 698 : *zeroed_any = rem_error & 1;
6898 698 : rem_error >>= 1;
6899 :
6900 698 : *ignored_any = rem_error & 1;
6901 698 : rem_error >>= 1;
6902 :
6903 698 : *zeroed_or_error_count = rem_error & READV_COUNT_MASK;
6904 698 : rem_error >>= READV_COUNT_BITS;
6905 :
6906 698 : *checkfail_count = rem_error & READV_COUNT_MASK;
6907 698 : rem_error >>= READV_COUNT_BITS;
6908 :
6909 698 : *first_off = rem_error & READV_COUNT_MASK;
6910 698 : rem_error >>= READV_COUNT_BITS;
6911 698 : }
6912 :
6913 : /*
6914 : * Helper to encode errors for buffer_readv_complete()
6915 : *
6916 : * Errors are encoded as follows:
6917 : * - bit 0 indicates whether any page was zeroed (1) or not (0)
6918 : * - bit 1 indicates whether any checksum failure was ignored (1) or not (0)
6919 : * - next READV_COUNT_BITS bits indicate the number of errored or zeroed pages
6920 : * - next READV_COUNT_BITS bits indicate the number of checksum failures
6921 : * - next READV_COUNT_BITS bits indicate the first offset of the first page
6922 : * that was errored or zeroed or, if no errors/zeroes, the first ignored
6923 : * checksum
6924 : */
6925 : static inline void
6926 384 : buffer_readv_encode_error(PgAioResult *result,
6927 : bool is_temp,
6928 : bool zeroed_any,
6929 : bool ignored_any,
6930 : uint8 error_count,
6931 : uint8 zeroed_count,
6932 : uint8 checkfail_count,
6933 : uint8 first_error_off,
6934 : uint8 first_zeroed_off,
6935 : uint8 first_ignored_off)
6936 : {
6937 :
6938 384 : uint8 shift = 0;
6939 384 : uint8 zeroed_or_error_count =
6940 : error_count > 0 ? error_count : zeroed_count;
6941 : uint8 first_off;
6942 :
6943 : StaticAssertStmt(PG_IOV_MAX <= 1 << READV_COUNT_BITS,
6944 : "PG_IOV_MAX is bigger than reserved space for error data");
6945 : StaticAssertStmt((1 + 1 + 3 * READV_COUNT_BITS) <= PGAIO_RESULT_ERROR_BITS,
6946 : "PGAIO_RESULT_ERROR_BITS is insufficient for buffer_readv");
6947 :
6948 : /*
6949 : * We only have space to encode one offset - but luckily that's good
6950 : * enough. If there is an error, the error is the interesting offset, same
6951 : * with a zeroed buffer vs an ignored buffer.
6952 : */
6953 384 : if (error_count > 0)
6954 188 : first_off = first_error_off;
6955 196 : else if (zeroed_count > 0)
6956 160 : first_off = first_zeroed_off;
6957 : else
6958 36 : first_off = first_ignored_off;
6959 :
6960 : Assert(!zeroed_any || error_count == 0);
6961 :
6962 384 : result->error_data = 0;
6963 :
6964 384 : result->error_data |= zeroed_any << shift;
6965 384 : shift += 1;
6966 :
6967 384 : result->error_data |= ignored_any << shift;
6968 384 : shift += 1;
6969 :
6970 384 : result->error_data |= ((uint32) zeroed_or_error_count) << shift;
6971 384 : shift += READV_COUNT_BITS;
6972 :
6973 384 : result->error_data |= ((uint32) checkfail_count) << shift;
6974 384 : shift += READV_COUNT_BITS;
6975 :
6976 384 : result->error_data |= ((uint32) first_off) << shift;
6977 384 : shift += READV_COUNT_BITS;
6978 :
6979 384 : result->id = is_temp ? PGAIO_HCB_LOCAL_BUFFER_READV :
6980 : PGAIO_HCB_SHARED_BUFFER_READV;
6981 :
6982 384 : if (error_count > 0)
6983 188 : result->status = PGAIO_RS_ERROR;
6984 : else
6985 196 : result->status = PGAIO_RS_WARNING;
6986 :
6987 : /*
6988 : * The encoding is complicated enough to warrant cross-checking it against
6989 : * the decode function.
6990 : */
6991 : #ifdef USE_ASSERT_CHECKING
6992 : {
6993 : bool zeroed_any_2,
6994 : ignored_any_2;
6995 : uint8 zeroed_or_error_count_2,
6996 : checkfail_count_2,
6997 : first_off_2;
6998 :
6999 : buffer_readv_decode_error(*result,
7000 : &zeroed_any_2, &ignored_any_2,
7001 : &zeroed_or_error_count_2,
7002 : &checkfail_count_2,
7003 : &first_off_2);
7004 : Assert(zeroed_any == zeroed_any_2);
7005 : Assert(ignored_any == ignored_any_2);
7006 : Assert(zeroed_or_error_count == zeroed_or_error_count_2);
7007 : Assert(checkfail_count == checkfail_count_2);
7008 : Assert(first_off == first_off_2);
7009 : }
7010 : #endif
7011 :
7012 : #undef READV_COUNT_BITS
7013 : #undef READV_COUNT_MASK
7014 384 : }
7015 :
7016 : /*
7017 : * Helper for AIO readv completion callbacks, supporting both shared and temp
7018 : * buffers. Gets called once for each buffer in a multi-page read.
7019 : */
7020 : static pg_attribute_always_inline void
7021 2507082 : buffer_readv_complete_one(PgAioTargetData *td, uint8 buf_off, Buffer buffer,
7022 : uint8 flags, bool failed, bool is_temp,
7023 : bool *buffer_invalid,
7024 : bool *failed_checksum,
7025 : bool *ignored_checksum,
7026 : bool *zeroed_buffer)
7027 : {
7028 2507082 : BufferDesc *buf_hdr = is_temp ?
7029 16806 : GetLocalBufferDescriptor(-buffer - 1)
7030 2507082 : : GetBufferDescriptor(buffer - 1);
7031 2507082 : BufferTag tag = buf_hdr->tag;
7032 2507082 : char *bufdata = BufferGetBlock(buffer);
7033 : uint32 set_flag_bits;
7034 : int piv_flags;
7035 :
7036 : /* check that the buffer is in the expected state for a read */
7037 : #ifdef USE_ASSERT_CHECKING
7038 : {
7039 : uint32 buf_state = pg_atomic_read_u32(&buf_hdr->state);
7040 :
7041 : Assert(buf_state & BM_TAG_VALID);
7042 : Assert(!(buf_state & BM_VALID));
7043 : /* temp buffers don't use BM_IO_IN_PROGRESS */
7044 : if (!is_temp)
7045 : Assert(buf_state & BM_IO_IN_PROGRESS);
7046 : Assert(!(buf_state & BM_DIRTY));
7047 : }
7048 : #endif
7049 :
7050 2507082 : *buffer_invalid = false;
7051 2507082 : *failed_checksum = false;
7052 2507082 : *ignored_checksum = false;
7053 2507082 : *zeroed_buffer = false;
7054 :
7055 : /*
7056 : * We ask PageIsVerified() to only log the message about checksum errors,
7057 : * as the completion might be run in any backend (or IO workers). We will
7058 : * report checksum errors in buffer_readv_report().
7059 : */
7060 2507082 : piv_flags = PIV_LOG_LOG;
7061 :
7062 : /* the local zero_damaged_pages may differ from the definer's */
7063 2507082 : if (flags & READ_BUFFERS_IGNORE_CHECKSUM_FAILURES)
7064 76 : piv_flags |= PIV_IGNORE_CHECKSUM_FAILURE;
7065 :
7066 : /* Check for garbage data. */
7067 2507082 : if (!failed)
7068 : {
7069 : /*
7070 : * If the buffer is not currently pinned by this backend, e.g. because
7071 : * we're completing this IO after an error, the buffer data will have
7072 : * been marked as inaccessible when the buffer was unpinned. The AIO
7073 : * subsystem holds a pin, but that doesn't prevent the buffer from
7074 : * having been marked as inaccessible. The completion might also be
7075 : * executed in a different process.
7076 : */
7077 : #ifdef USE_VALGRIND
7078 : if (!BufferIsPinned(buffer))
7079 : VALGRIND_MAKE_MEM_DEFINED(bufdata, BLCKSZ);
7080 : #endif
7081 :
7082 2507024 : if (!PageIsVerified((Page) bufdata, tag.blockNum, piv_flags,
7083 : failed_checksum))
7084 : {
7085 192 : if (flags & READ_BUFFERS_ZERO_ON_ERROR)
7086 : {
7087 92 : memset(bufdata, 0, BLCKSZ);
7088 92 : *zeroed_buffer = true;
7089 : }
7090 : else
7091 : {
7092 100 : *buffer_invalid = true;
7093 : /* mark buffer as having failed */
7094 100 : failed = true;
7095 : }
7096 : }
7097 2506832 : else if (*failed_checksum)
7098 24 : *ignored_checksum = true;
7099 :
7100 : /* undo what we did above */
7101 : #ifdef USE_VALGRIND
7102 : if (!BufferIsPinned(buffer))
7103 : VALGRIND_MAKE_MEM_NOACCESS(bufdata, BLCKSZ);
7104 : #endif
7105 :
7106 : /*
7107 : * Immediately log a message about the invalid page, but only to the
7108 : * server log. The reason to do so immediately is that this may be
7109 : * executed in a different backend than the one that originated the
7110 : * request. The reason to do so immediately is that the originator
7111 : * might not process the query result immediately (because it is busy
7112 : * doing another part of query processing) or at all (e.g. if it was
7113 : * cancelled or errored out due to another IO also failing). The
7114 : * definer of the IO will emit an ERROR or WARNING when processing the
7115 : * IO's results
7116 : *
7117 : * To avoid duplicating the code to emit these log messages, we reuse
7118 : * buffer_readv_report().
7119 : */
7120 2507024 : if (*buffer_invalid || *failed_checksum || *zeroed_buffer)
7121 : {
7122 216 : PgAioResult result_one = {0};
7123 :
7124 216 : buffer_readv_encode_error(&result_one, is_temp,
7125 216 : *zeroed_buffer,
7126 216 : *ignored_checksum,
7127 216 : *buffer_invalid,
7128 216 : *zeroed_buffer ? 1 : 0,
7129 216 : *failed_checksum ? 1 : 0,
7130 : buf_off, buf_off, buf_off);
7131 216 : pgaio_result_report(result_one, td, LOG_SERVER_ONLY);
7132 : }
7133 : }
7134 :
7135 : /* Terminate I/O and set BM_VALID. */
7136 2507082 : set_flag_bits = failed ? BM_IO_ERROR : BM_VALID;
7137 2507082 : if (is_temp)
7138 16806 : TerminateLocalBufferIO(buf_hdr, false, set_flag_bits, true);
7139 : else
7140 2490276 : TerminateBufferIO(buf_hdr, false, set_flag_bits, false, true);
7141 :
7142 : /*
7143 : * Call the BUFFER_READ_DONE tracepoint in the callback, even though the
7144 : * callback may not be executed in the same backend that called
7145 : * BUFFER_READ_START. The alternative would be to defer calling the
7146 : * tracepoint to a later point (e.g. the local completion callback for
7147 : * shared buffer reads), which seems even less helpful.
7148 : */
7149 : TRACE_POSTGRESQL_BUFFER_READ_DONE(tag.forkNum,
7150 : tag.blockNum,
7151 : tag.spcOid,
7152 : tag.dbOid,
7153 : tag.relNumber,
7154 : is_temp ? MyProcNumber : INVALID_PROC_NUMBER,
7155 : false);
7156 2507082 : }
7157 :
7158 : /*
7159 : * Perform completion handling of a single AIO read. This read may cover
7160 : * multiple blocks / buffers.
7161 : *
7162 : * Shared between shared and local buffers, to reduce code duplication.
7163 : */
7164 : static pg_attribute_always_inline PgAioResult
7165 2246232 : buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
7166 : uint8 cb_data, bool is_temp)
7167 : {
7168 2246232 : PgAioResult result = prior_result;
7169 2246232 : PgAioTargetData *td = pgaio_io_get_target_data(ioh);
7170 2246232 : uint8 first_error_off = 0;
7171 2246232 : uint8 first_zeroed_off = 0;
7172 2246232 : uint8 first_ignored_off = 0;
7173 2246232 : uint8 error_count = 0;
7174 2246232 : uint8 zeroed_count = 0;
7175 2246232 : uint8 ignored_count = 0;
7176 2246232 : uint8 checkfail_count = 0;
7177 : uint64 *io_data;
7178 : uint8 handle_data_len;
7179 :
7180 : if (is_temp)
7181 : {
7182 : Assert(td->smgr.is_temp);
7183 : Assert(pgaio_io_get_owner(ioh) == MyProcNumber);
7184 : }
7185 : else
7186 : Assert(!td->smgr.is_temp);
7187 :
7188 : /*
7189 : * Iterate over all the buffers affected by this IO and call the
7190 : * per-buffer completion function for each buffer.
7191 : */
7192 2246232 : io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
7193 4753314 : for (uint8 buf_off = 0; buf_off < handle_data_len; buf_off++)
7194 : {
7195 2507082 : Buffer buf = io_data[buf_off];
7196 : bool failed;
7197 2507082 : bool failed_verification = false;
7198 2507082 : bool failed_checksum = false;
7199 2507082 : bool zeroed_buffer = false;
7200 2507082 : bool ignored_checksum = false;
7201 :
7202 : Assert(BufferIsValid(buf));
7203 :
7204 : /*
7205 : * If the entire I/O failed on a lower-level, each buffer needs to be
7206 : * marked as failed. In case of a partial read, the first few buffers
7207 : * may be ok.
7208 : */
7209 2507082 : failed =
7210 2507082 : prior_result.status == PGAIO_RS_ERROR
7211 2507082 : || prior_result.result <= buf_off;
7212 :
7213 2507082 : buffer_readv_complete_one(td, buf_off, buf, cb_data, failed, is_temp,
7214 : &failed_verification,
7215 : &failed_checksum,
7216 : &ignored_checksum,
7217 : &zeroed_buffer);
7218 :
7219 : /*
7220 : * Track information about the number of different kinds of error
7221 : * conditions across all pages, as there can be multiple pages failing
7222 : * verification as part of one IO.
7223 : */
7224 2507082 : if (failed_verification && !zeroed_buffer && error_count++ == 0)
7225 88 : first_error_off = buf_off;
7226 2507082 : if (zeroed_buffer && zeroed_count++ == 0)
7227 68 : first_zeroed_off = buf_off;
7228 2507082 : if (ignored_checksum && ignored_count++ == 0)
7229 20 : first_ignored_off = buf_off;
7230 2507082 : if (failed_checksum)
7231 64 : checkfail_count++;
7232 : }
7233 :
7234 : /*
7235 : * If the smgr read succeeded [partially] and page verification failed for
7236 : * some of the pages, adjust the IO's result state appropriately.
7237 : */
7238 2246232 : if (prior_result.status != PGAIO_RS_ERROR &&
7239 2246126 : (error_count > 0 || ignored_count > 0 || zeroed_count > 0))
7240 : {
7241 168 : buffer_readv_encode_error(&result, is_temp,
7242 : zeroed_count > 0, ignored_count > 0,
7243 : error_count, zeroed_count, checkfail_count,
7244 : first_error_off, first_zeroed_off,
7245 : first_ignored_off);
7246 168 : pgaio_result_report(result, td, DEBUG1);
7247 : }
7248 :
7249 : /*
7250 : * For shared relations this reporting is done in
7251 : * shared_buffer_readv_complete_local().
7252 : */
7253 2246232 : if (is_temp && checkfail_count > 0)
7254 4 : pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
7255 : checkfail_count);
7256 :
7257 2246232 : return result;
7258 : }
7259 :
7260 : /*
7261 : * AIO error reporting callback for aio_shared_buffer_readv_cb and
7262 : * aio_local_buffer_readv_cb.
7263 : *
7264 : * The error is encoded / decoded in buffer_readv_encode_error() /
7265 : * buffer_readv_decode_error().
7266 : */
7267 : static void
7268 544 : buffer_readv_report(PgAioResult result, const PgAioTargetData *td,
7269 : int elevel)
7270 : {
7271 544 : int nblocks = td->smgr.nblocks;
7272 544 : BlockNumber first = td->smgr.blockNum;
7273 544 : BlockNumber last = first + nblocks - 1;
7274 544 : ProcNumber errProc =
7275 544 : td->smgr.is_temp ? MyProcNumber : INVALID_PROC_NUMBER;
7276 : RelPathStr rpath =
7277 544 : relpathbackend(td->smgr.rlocator, errProc, td->smgr.forkNum);
7278 : bool zeroed_any,
7279 : ignored_any;
7280 : uint8 zeroed_or_error_count,
7281 : checkfail_count,
7282 : first_off;
7283 : uint8 affected_count;
7284 : const char *msg_one,
7285 : *msg_mult,
7286 : *det_mult,
7287 : *hint_mult;
7288 :
7289 544 : buffer_readv_decode_error(result, &zeroed_any, &ignored_any,
7290 : &zeroed_or_error_count,
7291 : &checkfail_count,
7292 : &first_off);
7293 :
7294 : /*
7295 : * Treat a read that had both zeroed buffers *and* ignored checksums as a
7296 : * special case, it's too irregular to be emitted the same way as the
7297 : * other cases.
7298 : */
7299 544 : if (zeroed_any && ignored_any)
7300 : {
7301 : Assert(zeroed_any && ignored_any);
7302 : Assert(nblocks > 1); /* same block can't be both zeroed and ignored */
7303 : Assert(result.status != PGAIO_RS_ERROR);
7304 8 : affected_count = zeroed_or_error_count;
7305 :
7306 8 : ereport(elevel,
7307 : errcode(ERRCODE_DATA_CORRUPTED),
7308 : errmsg("zeroing %u page(s) and ignoring %u checksum failure(s) among blocks %u..%u of relation %s",
7309 : affected_count, checkfail_count, first, last, rpath.str),
7310 : affected_count > 1 ?
7311 : errdetail("Block %u held first zeroed page.",
7312 : first + first_off) : 0,
7313 : errhint("See server log for details about the other %d invalid block(s).",
7314 : affected_count + checkfail_count - 1));
7315 8 : return;
7316 : }
7317 :
7318 : /*
7319 : * The other messages are highly repetitive. To avoid duplicating a long
7320 : * and complicated ereport(), gather the translated format strings
7321 : * separately and then do one common ereport.
7322 : */
7323 536 : if (result.status == PGAIO_RS_ERROR)
7324 : {
7325 : Assert(!zeroed_any); /* can't have invalid pages when zeroing them */
7326 272 : affected_count = zeroed_or_error_count;
7327 272 : msg_one = _("invalid page in block %u of relation %s");
7328 272 : msg_mult = _("%u invalid pages among blocks %u..%u of relation %s");
7329 272 : det_mult = _("Block %u held first invalid page.");
7330 272 : hint_mult = _("See server log for the other %u invalid block(s).");
7331 : }
7332 264 : else if (zeroed_any && !ignored_any)
7333 : {
7334 216 : affected_count = zeroed_or_error_count;
7335 216 : msg_one = _("invalid page in block %u of relation %s; zeroing out page");
7336 216 : msg_mult = _("zeroing out %u invalid pages among blocks %u..%u of relation %s");
7337 216 : det_mult = _("Block %u held first zeroed page.");
7338 216 : hint_mult = _("See server log for the other %u zeroed block(s).");
7339 : }
7340 48 : else if (!zeroed_any && ignored_any)
7341 : {
7342 48 : affected_count = checkfail_count;
7343 48 : msg_one = _("ignoring checksum failure in block %u of relation %s");
7344 48 : msg_mult = _("ignoring %u checksum failures among blocks %u..%u of relation %s");
7345 48 : det_mult = _("Block %u held first ignored page.");
7346 48 : hint_mult = _("See server log for the other %u ignored block(s).");
7347 : }
7348 : else
7349 0 : pg_unreachable();
7350 :
7351 536 : ereport(elevel,
7352 : errcode(ERRCODE_DATA_CORRUPTED),
7353 : affected_count == 1 ?
7354 : errmsg_internal(msg_one, first + first_off, rpath.str) :
7355 : errmsg_internal(msg_mult, affected_count, first, last, rpath.str),
7356 : affected_count > 1 ? errdetail_internal(det_mult, first + first_off) : 0,
7357 : affected_count > 1 ? errhint_internal(hint_mult, affected_count - 1) : 0);
7358 : }
7359 :
7360 : static void
7361 2451716 : shared_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
7362 : {
7363 2451716 : buffer_stage_common(ioh, false, false);
7364 2451716 : }
7365 :
7366 : static PgAioResult
7367 2242632 : shared_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
7368 : uint8 cb_data)
7369 : {
7370 2242632 : return buffer_readv_complete(ioh, prior_result, cb_data, false);
7371 : }
7372 :
7373 : /*
7374 : * We need a backend-local completion callback for shared buffers, to be able
7375 : * to report checksum errors correctly. Unfortunately that can only safely
7376 : * happen if the reporting backend has previously called
7377 : * pgstat_prepare_report_checksum_failure(), which we can only guarantee in
7378 : * the backend that started the IO. Hence this callback.
7379 : */
7380 : static PgAioResult
7381 2451716 : shared_buffer_readv_complete_local(PgAioHandle *ioh, PgAioResult prior_result,
7382 : uint8 cb_data)
7383 : {
7384 : bool zeroed_any,
7385 : ignored_any;
7386 : uint8 zeroed_or_error_count,
7387 : checkfail_count,
7388 : first_off;
7389 :
7390 2451716 : if (prior_result.status == PGAIO_RS_OK)
7391 2451562 : return prior_result;
7392 :
7393 154 : buffer_readv_decode_error(prior_result,
7394 : &zeroed_any,
7395 : &ignored_any,
7396 : &zeroed_or_error_count,
7397 : &checkfail_count,
7398 : &first_off);
7399 :
7400 154 : if (checkfail_count)
7401 : {
7402 48 : PgAioTargetData *td = pgaio_io_get_target_data(ioh);
7403 :
7404 48 : pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
7405 : checkfail_count);
7406 : }
7407 :
7408 154 : return prior_result;
7409 : }
7410 :
7411 : static void
7412 3600 : local_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
7413 : {
7414 3600 : buffer_stage_common(ioh, false, true);
7415 3600 : }
7416 :
7417 : static PgAioResult
7418 3600 : local_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
7419 : uint8 cb_data)
7420 : {
7421 3600 : return buffer_readv_complete(ioh, prior_result, cb_data, true);
7422 : }
7423 :
7424 : /* readv callback is passed READ_BUFFERS_* flags as callback data */
7425 : const PgAioHandleCallbacks aio_shared_buffer_readv_cb = {
7426 : .stage = shared_buffer_readv_stage,
7427 : .complete_shared = shared_buffer_readv_complete,
7428 : /* need a local callback to report checksum failures */
7429 : .complete_local = shared_buffer_readv_complete_local,
7430 : .report = buffer_readv_report,
7431 : };
7432 :
7433 : /* readv callback is passed READ_BUFFERS_* flags as callback data */
7434 : const PgAioHandleCallbacks aio_local_buffer_readv_cb = {
7435 : .stage = local_buffer_readv_stage,
7436 :
7437 : /*
7438 : * Note that this, in contrast to the shared_buffers case, uses
7439 : * complete_local, as only the issuing backend has access to the required
7440 : * datastructures. This is important in case the IO completion may be
7441 : * consumed incidentally by another backend.
7442 : */
7443 : .complete_local = local_buffer_readv_complete,
7444 : .report = buffer_readv_report,
7445 : };
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