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Fixing possible losing data changes: 

1. New flag - BM_JUST_DIRTIED - added for BufferDesc;
2. All data "dirtiers" (WriteBuffer and WriteNoReleaseBuffer)
   set this flag (and BM_DIRTY too);
3. All data "flushers" (FlushBuffer, BufferSync and BufferReplace)
   turn this flag off just before calling smgr[blind]write/smgrflush
   and check this flag after flushing buffer: if it turned ON then
   BM_DIRTY will stay ON.
This commit is contained in:
Vadim B. Mikheev 1997-01-20 04:36:48 +00:00
parent deef313fd0
commit 9ff69034b2
1 changed files with 62 additions and 15 deletions
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77
src/backend/storage/buffer/bufmgr.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.8 1997/01/16 08:11:41 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.9 1997/01/20 04:36:48 vadim Exp $
*
*-------------------------------------------------------------------------
*/
@ -474,7 +474,19 @@ BufferAlloc(Relation reln,
else
{
BufferFlushCount++;
buf->flags &= ~BM_DIRTY;
/*
* BM_JUST_DIRTIED cleared by BufferReplace and shouldn't
* be setted by anyone. - vadim 01/17/97
*/
if ( buf->flags & BM_JUST_DIRTIED )
{
elog (FATAL, "BufferAlloc: content of block %u (%s) changed while flushing",
buf->tag.blockNum, buf->sb_relname);
}
else
{
buf->flags &= ~BM_DIRTY;
}
}
/*
@ -488,7 +500,8 @@ BufferAlloc(Relation reln,
* no reason to think that we have an immediate disaster on
* our hands.
*/
if (buf && buf->refcount > 1) {
if ( buf && buf->refcount > 1 )
{
inProgress = FALSE;
buf->flags &= ~BM_IO_IN_PROGRESS;
#ifdef HAS_TEST_AND_SET
@ -643,7 +656,7 @@ WriteBuffer(Buffer buffer)
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= BM_DIRTY;
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
UnpinBuffer(bufHdr);
SpinRelease(BufMgrLock);
}
@ -733,19 +746,36 @@ FlushBuffer(Buffer buffer, bool release)
bufrel = RelationIdCacheGetRelation (bufHdr->tag.relId.relId);
Assert (bufrel != (Relation) NULL);
/* To check if block content changed while flushing. - vadim 01/17/97 */
SpinAcquire(BufMgrLock);
bufHdr->flags &= ~BM_JUST_DIRTIED;
SpinRelease(BufMgrLock);
status = smgrflush(bufHdr->bufsmgr, bufrel, bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
if (status == SM_FAIL)
{
elog(WARN, "FlushBuffer: cannot flush block %u of the relation %.*s",
bufHdr->tag.blockNum,
NAMEDATALEN, bufrel->rd_rel->relname.data);
elog(WARN, "FlushBuffer: cannot flush block %u of the relation %s",
bufHdr->tag.blockNum, bufHdr->sb_relname);
return (STATUS_ERROR);
}
SpinAcquire(BufMgrLock);
bufHdr->flags &= ~BM_DIRTY;
/*
* If this buffer was marked by someone as DIRTY while
* we were flushing it out we must not clear DIRTY flag
* - vadim 01/17/97
*/
if ( bufHdr->flags & BM_JUST_DIRTIED )
{
elog (NOTICE, "FlusfBuffer: content of block %u (%s) changed while flushing",
bufHdr->tag.blockNum, bufHdr->sb_relname);
}
else
{
bufHdr->flags &= ~BM_DIRTY;
}
if ( release )
UnpinBuffer(bufHdr);
SpinRelease(BufMgrLock);
@ -779,7 +809,7 @@ WriteNoReleaseBuffer(Buffer buffer)
bufHdr = &BufferDescriptors[buffer-1];
SpinAcquire(BufMgrLock);
bufHdr->flags |= BM_DIRTY;
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
SpinRelease(BufMgrLock);
}
return(STATUS_OK);
@ -878,13 +908,19 @@ BufferSync()
UnpinBuffer(bufHdr);
if (bufHdr->flags & BM_IO_ERROR)
{
elog(WARN, "cannot write %u for %s",
elog(WARN, "BufferSync: write error %u for %s",
bufHdr->tag.blockNum, bufHdr->sb_relname);
}
if (reln != (Relation)NULL)
RelationDecrementReferenceCount(reln);
continue;
}
/*
* To check if block content changed while flushing
* (see below). - vadim 01/17/97
*/
bufHdr->flags &= ~BM_JUST_DIRTIED;
/*
* If we didn't have the reldesc in our local cache, flush this
@ -912,15 +948,23 @@ BufferSync()
UnpinBuffer(bufHdr);
if (status == SM_FAIL) {
bufHdr->flags |= BM_IO_ERROR;
elog(WARN, "cannot write %u for %s",
elog(WARN, "BufferSync: cannot write %u for %s",
bufHdr->tag.blockNum, bufHdr->sb_relname);
}
/*
* What if someone has marked this buffer as DIRTY after
* smgr[blind]write but before SpinAcquire(BufMgrLock)
* ??? - vadim 01/16/97
* If this buffer was marked by someone as DIRTY while
* we were flushing it out we must not clear DIRTY flag
* - vadim 01/17/97
*/
bufHdr->flags &= ~BM_DIRTY;
if ( bufHdr->flags & BM_JUST_DIRTIED )
{
elog (NOTICE, "BufferSync: content of block %u (%s) changed while flushing",
bufHdr->tag.blockNum, bufHdr->sb_relname);
}
else
{
bufHdr->flags &= ~BM_DIRTY;
}
if (reln != (Relation)NULL)
RelationDecrementReferenceCount(reln);
}
@ -1189,6 +1233,9 @@ BufferReplace(BufferDesc *bufHdr, bool bufferLockHeld)
reln = RelationIdCacheGetRelation(bufrel);
else
reln = (Relation) NULL;
/* To check if block content changed while flushing. - vadim 01/17/97 */
bufHdr->flags &= ~BM_JUST_DIRTIED;
SpinRelease(BufMgrLock);