TLA  Line data    Source code

       1                 : /*-------------------------------------------------------------------------
       2                 :  *
       3                 :  * sharedfileset.c
       4                 :  *    Shared temporary file management.
       5                 :  *
       6                 :  * Portions Copyright (c) 1996-2023, 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/ipc.h"
      29                 : #include "storage/sharedfileset.h"
      30                 : #include "utils/builtins.h"
      31                 : 
      32                 : static void SharedFileSetOnDetach(dsm_segment *segment, Datum datum);
      33                 : 
      34                 : /*
      35                 :  * Initialize a space for temporary files that can be opened by other backends.
      36                 :  * Other backends must attach to it before accessing it.  Associate this
      37                 :  * SharedFileSet with 'seg'.  Any contained files will be deleted when the
      38                 :  * last backend detaches.
      39                 :  *
      40                 :  * Under the covers the set is one or more directories which will eventually
      41                 :  * be deleted.
      42                 :  */
      43                 : void
      44 CBC         160 : SharedFileSetInit(SharedFileSet *fileset, dsm_segment *seg)
      45                 : {
      46                 :     /* Initialize the shared fileset specific members. */
      47             160 :     SpinLockInit(&fileset->mutex);
      48             160 :     fileset->refcnt = 1;
      49                 : 
      50                 :     /* Initialize the fileset. */
      51             160 :     FileSetInit(&fileset->fs);
      52                 : 
      53                 :     /* Register our cleanup callback. */
      54             160 :     if (seg)
      55             160 :         on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
      56             160 : }
      57                 : 
      58                 : /*
      59                 :  * Attach to a set of directories that was created with SharedFileSetInit.
      60                 :  */
      61                 : void
      62             250 : SharedFileSetAttach(SharedFileSet *fileset, dsm_segment *seg)
      63                 : {
      64                 :     bool        success;
      65                 : 
      66             250 :     SpinLockAcquire(&fileset->mutex);
      67             250 :     if (fileset->refcnt == 0)
      68 UBC           0 :         success = false;
      69                 :     else
      70                 :     {
      71 CBC         250 :         ++fileset->refcnt;
      72             250 :         success = true;
      73                 :     }
      74             250 :     SpinLockRelease(&fileset->mutex);
      75                 : 
      76             250 :     if (!success)
      77 UBC           0 :         ereport(ERROR,
      78                 :                 (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
      79                 :                  errmsg("could not attach to a SharedFileSet that is already destroyed")));
      80                 : 
      81                 :     /* Register our cleanup callback. */
      82 CBC         250 :     on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
      83             250 : }
      84                 : 
      85                 : /*
      86                 :  * Delete all files in the set.
      87                 :  */
      88                 : void
      89              24 : SharedFileSetDeleteAll(SharedFileSet *fileset)
      90                 : {
      91              24 :     FileSetDeleteAll(&fileset->fs);
      92              24 : }
      93                 : 
      94                 : /*
      95                 :  * Callback function that will be invoked when this backend detaches from a
      96                 :  * DSM segment holding a SharedFileSet that it has created or attached to.  If
      97                 :  * we are the last to detach, then try to remove the directories and
      98                 :  * everything in them.  We can't raise an error on failures, because this runs
      99                 :  * in error cleanup paths.
     100                 :  */
     101                 : static void
     102             410 : SharedFileSetOnDetach(dsm_segment *segment, Datum datum)
     103                 : {
     104             410 :     bool        unlink_all = false;
     105             410 :     SharedFileSet *fileset = (SharedFileSet *) DatumGetPointer(datum);
     106                 : 
     107             410 :     SpinLockAcquire(&fileset->mutex);
     108             410 :     Assert(fileset->refcnt > 0);
     109             410 :     if (--fileset->refcnt == 0)
     110             160 :         unlink_all = true;
     111             410 :     SpinLockRelease(&fileset->mutex);
     112                 : 
     113                 :     /*
     114                 :      * If we are the last to detach, we delete the directory in all
     115                 :      * tablespaces.  Note that we are still actually attached for the rest of
     116                 :      * this function so we can safely access its data.
     117                 :      */
     118             410 :     if (unlink_all)
     119             160 :         FileSetDeleteAll(&fileset->fs);
     120             410 : }