From e0058b61728438469898845be0a7afb73f2ebc86 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Tue, 21 Jul 1998 04:17:30 +0000
Subject: [PATCH] Theses buffer leaks are caused by indexes that are kept open
between calls. Outside a transaction, the backend detects them as buffer
leaks; it sends a NOTICE, and frees them. This sometimes cause a segmentation
fault (at least on Linux). These indexes are initialized on the first
lo_read/lo_write/lo_tell call, and (normally) closed on a lo_close call.
Thus the buffer leaks appear when lo direct access functions are used, and
not with lo_import/lo_export functions (libpq version calls lo_close before
ending the command, and the backend version uses another path).
The included patches (against recent snapshot, and against 6.3.2)
cause indexes to be closed on transaction end (that is on explicit
'END' statment, or on command termination outside trasaction blocks),
thus preventing the buffer leaks while increasing performance inside
transactions. Some (all?) 'classic' memory leaks are also removed.
I hope it will be ok.
--- Pascal ANDRE, graduated from Ecole Centrale Paris andre@via.ecp.fr
---
src/backend/access/transam/xact.c | 14 +++++-
src/backend/libpq/be-fsstubs.c | 25 +++++++++-
src/backend/storage/large_object/inv_api.c | 54 ++++++++++++++++++++--
src/include/libpq/be-fsstubs.h | 7 ++-
src/include/storage/large_object.h | 5 +-
5 files changed, 96 insertions(+), 9 deletions(-)
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index fb888640a99..f32a7fb00b5 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.20 1998/06/15 19:28:02 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.21 1998/07/21 04:17:21 momjian Exp $
*
* NOTES
* Transaction aborts can now occur two ways:
@@ -137,6 +137,11 @@
*-------------------------------------------------------------------------
*/
+/*
+ * Large object clean up added in CommitTransaction() to prevent buffer leaks.
+ * [PA, 7/17/98]
+ * [PA] is Pascal André <andre@via.ecp.fr>
+ */
#include <postgres.h>
#include <access/xact.h>
@@ -151,6 +156,9 @@
#include <commands/async.h>
#include <commands/sequence.h>
+/* included for _lo_commit [PA, 7/17/98] */
+#include <libpq/be-fsstubs.h>
+
static void AbortTransaction(void);
static void AtAbort_Cache(void);
static void AtAbort_Locks(void);
@@ -889,6 +897,10 @@ CommitTransaction()
* do commit processing
* ----------------
*/
+
+ /* handle commit for large objects [ PA, 7/17/98 ] */
+ _lo_commit();
+
CloseSequences();
DestroyTempRels();
AtEOXact_portals();
diff --git a/src/backend/libpq/be-fsstubs.c b/src/backend/libpq/be-fsstubs.c
index 8ecf45fe122..5267cf40abe 100644
--- a/src/backend/libpq/be-fsstubs.c
+++ b/src/backend/libpq/be-fsstubs.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/libpq/be-fsstubs.c,v 1.21 1998/06/15 19:28:25 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/libpq/be-fsstubs.c,v 1.22 1998/07/21 04:17:23 momjian Exp $
*
* NOTES
* This should be moved to a more appropriate place. It is here
@@ -41,6 +41,8 @@
#include <storage/large_object.h>
#include <libpq/be-fsstubs.h>
+/* [PA] is Pascal André <andre@via.ecp.fr> */
+
/*#define FSDB 1*/
#define MAX_LOBJ_FDS 256
@@ -52,7 +54,6 @@ static GlobalMemory fscxt = NULL;
static int newLOfd(LargeObjectDesc *lobjCookie);
static void deleteLOfd(int fd);
-
/*****************************************************************************
* File Interfaces for Large Objects
*****************************************************************************/
@@ -367,6 +368,26 @@ lo_export(Oid lobjId, text *filename)
return 1;
}
+/*
+ * lo_commit -
+ * prepares large objects for transaction commit [PA, 7/17/98]
+ */
+void
+_lo_commit(void)
+{
+ int i;
+ MemoryContext currentContext;
+
+ currentContext = MemoryContextSwitchTo((MemoryContext) fscxt);
+
+ for (i = 0; i < MAX_LOBJ_FDS; i++) {
+ if (cookies[i] != NULL) inv_cleanindex(cookies[i]);
+ }
+
+ MemoryContextSwitchTo(currentContext);
+
+}
+
/*****************************************************************************
* Support routines for this file
diff --git a/src/backend/storage/large_object/inv_api.c b/src/backend/storage/large_object/inv_api.c
index c3d63ac36b2..e92c75f0a34 100644
--- a/src/backend/storage/large_object/inv_api.c
+++ b/src/backend/storage/large_object/inv_api.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.30 1998/06/15 19:29:16 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.31 1998/07/21 04:17:24 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -60,6 +60,19 @@
* for data.
*/
+/*
+ * In order to prevent buffer leak on transaction commit, large object
+ * scan index handling has been modified. Indexes are persistant inside
+ * a transaction but may be closed between two calls to this API (when
+ * transaction is committed while object is opened, or when no
+ * transaction is active). Scan indexes are thus now reinitialized using
+ * the object current offset. [PA]
+ *
+ * Some cleanup has been also done for non freed memory.
+ *
+ * For subsequent notes, [PA] is Pascal André <andre@via.ecp.fr>
+ */
+
#define IFREESPC(p) (PageGetFreeSpace(p) - sizeof(HeapTupleData) - sizeof(struct varlena) - sizeof(int32))
#define IMAXBLK 8092
#define IMINBLK 512
@@ -261,8 +274,11 @@ inv_close(LargeObjectDesc *obj_desc)
{
Assert(PointerIsValid(obj_desc));
- if (obj_desc->iscan != (IndexScanDesc) NULL)
+ if (obj_desc->iscan != (IndexScanDesc) NULL) {
index_endscan(obj_desc->iscan);
+ pfree(obj_desc->iscan);
+ obj_desc->iscan = NULL;
+ }
heap_close(obj_desc->heap_r);
index_close(obj_desc->index_r);
@@ -546,6 +562,28 @@ inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes)
return (nwritten);
}
+/*
+ * inv_cleanindex --
+ * Clean opened indexes for large objects, and clears current result.
+ * This is necessary on transaction commit in order to prevent buffer
+ * leak.
+ * This function must be called for each opened large object.
+ * [ PA, 7/17/98 ]
+ */
+void
+inv_cleanindex(LargeObjectDesc *obj_desc)
+{
+ Assert(PointerIsValid(obj_desc));
+
+ if (obj_desc->iscan == (IndexScanDesc) NULL) return;
+
+ index_endscan(obj_desc->iscan);
+ pfree(obj_desc->iscan);
+ obj_desc->iscan = (IndexScanDesc) NULL;
+
+ ItemPointerSetInvalid(&(obj_desc->htid));
+}
+
/*
* inv_fetchtup -- Fetch an inversion file system block.
*
@@ -591,8 +629,13 @@ inv_fetchtup(LargeObjectDesc *obj_desc, Buffer *bufP)
{
ScanKeyData skey;
+ /*
+ * As scan index may be prematurely closed (on commit),
+ * we must use object current offset (was 0) to
+ * reinitialize the entry [ PA ].
+ */
ScanKeyEntryInitialize(&skey, 0x0, 1, F_INT4GE,
- Int32GetDatum(0));
+ Int32GetDatum(obj_desc->offset));
obj_desc->iscan =
index_beginscan(obj_desc->index_r,
(bool) 0, (uint16) 1,
@@ -622,7 +665,7 @@ inv_fetchtup(LargeObjectDesc *obj_desc, Buffer *bufP)
/* remember this tid -- we may need it for later reads/writes */
ItemPointerCopy(&(res->heap_iptr), &(obj_desc->htid));
-
+ pfree(res);
}
else
{
@@ -1179,6 +1222,7 @@ _inv_getsize(Relation hreln, TupleDesc hdesc, Relation ireln)
if (res == (RetrieveIndexResult) NULL)
{
index_endscan(iscan);
+ pfree(iscan);
return (0);
}
@@ -1192,11 +1236,13 @@ _inv_getsize(Relation hreln, TupleDesc hdesc, Relation ireln)
ReleaseBuffer(buf);
htup = heap_fetch(hreln, false, &(res->heap_iptr), &buf);
+ pfree(res);
} while (!HeapTupleIsValid(htup));
/* don't need the index scan anymore */
index_endscan(iscan);
+ pfree(iscan);
/* get olastbyte attribute */
d = heap_getattr(htup, 1, hdesc, &isNull);
diff --git a/src/include/libpq/be-fsstubs.h b/src/include/libpq/be-fsstubs.h
index 507f2a93677..108869dac95 100644
--- a/src/include/libpq/be-fsstubs.h
+++ b/src/include/libpq/be-fsstubs.h
@@ -6,7 +6,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
- * $Id: be-fsstubs.h,v 1.5 1997/09/08 21:52:33 momjian Exp $
+ * $Id: be-fsstubs.h,v 1.6 1998/07/21 04:17:26 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -37,4 +37,9 @@ extern int lo_unlink(Oid lobjId);
extern struct varlena *loread(int fd, int len);
extern int lowrite(int fd, struct varlena * wbuf);
+/*
+ * Added for buffer leak prevention [ Pascal André <andre@via.ecp.fr> ]
+ */
+extern void _lo_commit(void);
+
#endif /* BE_FSSTUBS_H */
diff --git a/src/include/storage/large_object.h b/src/include/storage/large_object.h
index 276792e19e2..3d35dba907a 100644
--- a/src/include/storage/large_object.h
+++ b/src/include/storage/large_object.h
@@ -7,7 +7,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
- * $Id: large_object.h,v 1.7 1997/09/08 21:54:29 momjian Exp $
+ * $Id: large_object.h,v 1.8 1998/07/21 04:17:30 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -54,4 +54,7 @@ extern int inv_tell(LargeObjectDesc *obj_desc);
extern int inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes);
extern int inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes);
+/* added for buffer leak prevention [ PA ] */
+extern void inv_cleanindex(LargeObjectDesc *obj_desc);
+
#endif /* LARGE_OBJECT_H */
--
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