Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * sharedfileset.c
4 : * Shared temporary file management.
5 : *
6 : * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * IDENTIFICATION
10 : * src/backend/storage/file/sharedfileset.c
11 : *
12 : * SharedFileSets provide a temporary namespace (think directory) so that
13 : * files can be discovered by name, and a shared ownership semantics so that
14 : * shared files survive until the last user detaches.
15 : *
16 : *-------------------------------------------------------------------------
17 : */
18 :
19 : #include "postgres.h"
20 :
21 : #include <limits.h>
22 :
23 : #include "catalog/pg_tablespace.h"
24 : #include "commands/tablespace.h"
25 : #include "common/hashfn.h"
26 : #include "miscadmin.h"
27 : #include "storage/dsm.h"
28 : #include "storage/sharedfileset.h"
29 : #include "utils/builtins.h"
30 :
31 : static void SharedFileSetOnDetach(dsm_segment *segment, Datum datum);
32 : static void SharedFileSetPath(char *path, SharedFileSet *fileset, Oid tablespace);
33 : static void SharedFilePath(char *path, SharedFileSet *fileset, const char *name);
34 : static Oid ChooseTablespace(const SharedFileSet *fileset, const char *name);
35 :
36 : /*
37 : * Initialize a space for temporary files that can be opened for read-only
38 : * access by other backends. Other backends must attach to it before
39 : * accessing it. Associate this SharedFileSet with 'seg'. Any contained
40 : * files will be deleted when the last backend detaches.
41 : *
42 : * Files will be distributed over the tablespaces configured in
43 : * temp_tablespaces.
44 : *
45 : * Under the covers the set is one or more directories which will eventually
46 : * be deleted when there are no backends attached.
47 : */
48 : void
49 188 : SharedFileSetInit(SharedFileSet *fileset, dsm_segment *seg)
50 : {
51 : static uint32 counter = 0;
52 :
53 188 : SpinLockInit(&fileset->mutex);
54 188 : fileset->refcnt = 1;
55 188 : fileset->creator_pid = MyProcPid;
56 188 : fileset->number = counter;
57 188 : counter = (counter + 1) % INT_MAX;
58 :
59 : /* Capture the tablespace OIDs so that all backends agree on them. */
60 188 : PrepareTempTablespaces();
61 188 : fileset->ntablespaces =
62 188 : GetTempTablespaces(&fileset->tablespaces[0],
63 : lengthof(fileset->tablespaces));
64 188 : if (fileset->ntablespaces == 0)
65 : {
66 188 : fileset->tablespaces[0] = DEFAULTTABLESPACE_OID;
67 188 : fileset->ntablespaces = 1;
68 : }
69 :
70 : /* Register our cleanup callback. */
71 188 : on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
72 188 : }
73 :
74 : /*
75 : * Attach to a set of directories that was created with SharedFileSetInit.
76 : */
77 : void
78 304 : SharedFileSetAttach(SharedFileSet *fileset, dsm_segment *seg)
79 : {
80 : bool success;
81 :
82 304 : SpinLockAcquire(&fileset->mutex);
83 304 : if (fileset->refcnt == 0)
84 0 : success = false;
85 : else
86 : {
87 304 : ++fileset->refcnt;
88 304 : success = true;
89 : }
90 304 : SpinLockRelease(&fileset->mutex);
91 :
92 304 : if (!success)
93 0 : ereport(ERROR,
94 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
95 : errmsg("could not attach to a SharedFileSet that is already destroyed")));
96 :
97 : /* Register our cleanup callback. */
98 304 : on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
99 304 : }
100 :
101 : /*
102 : * Create a new file in the given set.
103 : */
104 : File
105 1406 : SharedFileSetCreate(SharedFileSet *fileset, const char *name)
106 : {
107 : char path[MAXPGPATH];
108 : File file;
109 :
110 1406 : SharedFilePath(path, fileset, name);
111 1406 : file = PathNameCreateTemporaryFile(path, false);
112 :
113 : /* If we failed, see if we need to create the directory on demand. */
114 1406 : if (file <= 0)
115 : {
116 : char tempdirpath[MAXPGPATH];
117 : char filesetpath[MAXPGPATH];
118 184 : Oid tablespace = ChooseTablespace(fileset, name);
119 :
120 184 : TempTablespacePath(tempdirpath, tablespace);
121 184 : SharedFileSetPath(filesetpath, fileset, tablespace);
122 184 : PathNameCreateTemporaryDir(tempdirpath, filesetpath);
123 184 : file = PathNameCreateTemporaryFile(path, true);
124 : }
125 :
126 1406 : return file;
127 : }
128 :
129 : /*
130 : * Open a file that was created with SharedFileSetCreate(), possibly in
131 : * another backend.
132 : */
133 : File
134 2724 : SharedFileSetOpen(SharedFileSet *fileset, const char *name)
135 : {
136 : char path[MAXPGPATH];
137 : File file;
138 :
139 2724 : SharedFilePath(path, fileset, name);
140 2724 : file = PathNameOpenTemporaryFile(path);
141 :
142 2724 : return file;
143 : }
144 :
145 : /*
146 : * Delete a file that was created with SharedFileSetCreate().
147 : * Return true if the file existed, false if didn't.
148 : */
149 : bool
150 1406 : SharedFileSetDelete(SharedFileSet *fileset, const char *name,
151 : bool error_on_failure)
152 : {
153 : char path[MAXPGPATH];
154 :
155 1406 : SharedFilePath(path, fileset, name);
156 :
157 1406 : return PathNameDeleteTemporaryFile(path, error_on_failure);
158 : }
159 :
160 : /*
161 : * Delete all files in the set.
162 : */
163 : void
164 220 : SharedFileSetDeleteAll(SharedFileSet *fileset)
165 : {
166 : char dirpath[MAXPGPATH];
167 : int i;
168 :
169 : /*
170 : * Delete the directory we created in each tablespace. Doesn't fail
171 : * because we use this in error cleanup paths, but can generate LOG
172 : * message on IO error.
173 : */
174 440 : for (i = 0; i < fileset->ntablespaces; ++i)
175 : {
176 220 : SharedFileSetPath(dirpath, fileset, fileset->tablespaces[i]);
177 220 : PathNameDeleteTemporaryDir(dirpath);
178 : }
179 220 : }
180 :
181 : /*
182 : * Callback function that will be invoked when this backend detaches from a
183 : * DSM segment holding a SharedFileSet that it has created or attached to. If
184 : * we are the last to detach, then try to remove the directories and
185 : * everything in them. We can't raise an error on failures, because this runs
186 : * in error cleanup paths.
187 : */
188 : static void
189 492 : SharedFileSetOnDetach(dsm_segment *segment, Datum datum)
190 : {
191 492 : bool unlink_all = false;
192 492 : SharedFileSet *fileset = (SharedFileSet *) DatumGetPointer(datum);
193 :
194 492 : SpinLockAcquire(&fileset->mutex);
195 : Assert(fileset->refcnt > 0);
196 492 : if (--fileset->refcnt == 0)
197 188 : unlink_all = true;
198 492 : SpinLockRelease(&fileset->mutex);
199 :
200 : /*
201 : * If we are the last to detach, we delete the directory in all
202 : * tablespaces. Note that we are still actually attached for the rest of
203 : * this function so we can safely access its data.
204 : */
205 492 : if (unlink_all)
206 188 : SharedFileSetDeleteAll(fileset);
207 492 : }
208 :
209 : /*
210 : * Build the path for the directory holding the files backing a SharedFileSet
211 : * in a given tablespace.
212 : */
213 : static void
214 5940 : SharedFileSetPath(char *path, SharedFileSet *fileset, Oid tablespace)
215 : {
216 : char tempdirpath[MAXPGPATH];
217 :
218 5940 : TempTablespacePath(tempdirpath, tablespace);
219 11880 : snprintf(path, MAXPGPATH, "%s/%s%lu.%u.sharedfileset",
220 : tempdirpath, PG_TEMP_FILE_PREFIX,
221 5940 : (unsigned long) fileset->creator_pid, fileset->number);
222 5940 : }
223 :
224 : /*
225 : * Sorting hat to determine which tablespace a given shared temporary file
226 : * belongs in.
227 : */
228 : static Oid
229 5720 : ChooseTablespace(const SharedFileSet *fileset, const char *name)
230 : {
231 5720 : uint32 hash = hash_any((const unsigned char *) name, strlen(name));
232 :
233 5720 : return fileset->tablespaces[hash % fileset->ntablespaces];
234 : }
235 :
236 : /*
237 : * Compute the full path of a file in a SharedFileSet.
238 : */
239 : static void
240 5536 : SharedFilePath(char *path, SharedFileSet *fileset, const char *name)
241 : {
242 : char dirpath[MAXPGPATH];
243 :
244 5536 : SharedFileSetPath(dirpath, fileset, ChooseTablespace(fileset, name));
245 5536 : snprintf(path, MAXPGPATH, "%s/%s", dirpath, name);
246 5536 : }
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