121 lines
3.3 KiB
C
121 lines
3.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* sharedfileset.c
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* Shared temporary file management.
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*
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* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/backend/storage/file/sharedfileset.c
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*
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* SharedFileSets provide a temporary namespace (think directory) so that
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* files can be discovered by name, and a shared ownership semantics so that
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* shared files survive until the last user detaches.
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <limits.h>
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#include "catalog/pg_tablespace.h"
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#include "commands/tablespace.h"
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#include "common/hashfn.h"
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#include "miscadmin.h"
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#include "storage/dsm.h"
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#include "storage/ipc.h"
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#include "storage/sharedfileset.h"
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#include "utils/builtins.h"
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static void SharedFileSetOnDetach(dsm_segment *segment, Datum datum);
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/*
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* Initialize a space for temporary files that can be opened by other backends.
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* Other backends must attach to it before accessing it. Associate this
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* SharedFileSet with 'seg'. Any contained files will be deleted when the
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* last backend detaches.
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*
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* Under the covers the set is one or more directories which will eventually
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* be deleted.
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*/
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void
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SharedFileSetInit(SharedFileSet *fileset, dsm_segment *seg)
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{
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/* Initialize the shared fileset specific members. */
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SpinLockInit(&fileset->mutex);
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fileset->refcnt = 1;
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/* Initialize the fileset. */
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FileSetInit(&fileset->fs);
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/* Register our cleanup callback. */
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if (seg)
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on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
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}
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/*
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* Attach to a set of directories that was created with SharedFileSetInit.
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*/
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void
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SharedFileSetAttach(SharedFileSet *fileset, dsm_segment *seg)
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{
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bool success;
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SpinLockAcquire(&fileset->mutex);
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if (fileset->refcnt == 0)
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success = false;
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else
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{
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++fileset->refcnt;
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success = true;
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}
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SpinLockRelease(&fileset->mutex);
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if (!success)
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("could not attach to a SharedFileSet that is already destroyed")));
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/* Register our cleanup callback. */
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on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
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}
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/*
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* Delete all files in the set.
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*/
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void
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SharedFileSetDeleteAll(SharedFileSet *fileset)
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{
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FileSetDeleteAll(&fileset->fs);
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}
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/*
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* Callback function that will be invoked when this backend detaches from a
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* DSM segment holding a SharedFileSet that it has created or attached to. If
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* we are the last to detach, then try to remove the directories and
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* everything in them. We can't raise an error on failures, because this runs
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* in error cleanup paths.
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*/
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static void
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SharedFileSetOnDetach(dsm_segment *segment, Datum datum)
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{
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bool unlink_all = false;
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SharedFileSet *fileset = (SharedFileSet *) DatumGetPointer(datum);
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SpinLockAcquire(&fileset->mutex);
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Assert(fileset->refcnt > 0);
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if (--fileset->refcnt == 0)
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unlink_all = true;
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SpinLockRelease(&fileset->mutex);
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/*
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* If we are the last to detach, we delete the directory in all
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* tablespaces. Note that we are still actually attached for the rest of
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* this function so we can safely access its data.
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*/
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if (unlink_all)
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FileSetDeleteAll(&fileset->fs);
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}
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