Clean up WAL/buffer interactions as per my recent proposal. Get rid of the

misleadingly-named WriteBuffer routine, and instead require routines that
change buffer pages to call MarkBufferDirty (which does exactly what it says).
We also require that they do so before calling XLogInsert; this takes care of
the synchronization requirement documented in SyncOneBuffer.  Note that
because bufmgr takes the buffer content lock (in shared mode) while writing
out any buffer, it doesn't matter whether MarkBufferDirty is executed before
the buffer content change is complete, so long as the content change is
completed before releasing exclusive lock on the buffer.  So it's OK to set
the dirtybit before we fill in the LSN.
This eliminates the former kluge of needing to set the dirtybit in LockBuffer.
Aside from making the code more transparent, we can also add some new
debugging assertions, in particular that the caller of MarkBufferDirty must
hold the buffer content lock, not merely a pin.

1 files changed, 21 insertions, 26 deletions

diff --git a/src/backend/access/gist/gistvacuum.c b/src/backend/access/gist/gistvacuum.c
index e7925c2c151..285f1301321 100644
--- a/src/backend/access/gist/gistvacuum.c
+++ b/src/backend/access/gist/gistvacuum.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/gist/gistvacuum.c,v 1.17 2006/03/30 23:03:10 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/gist/gistvacuum.c,v 1.18 2006/03/31 23:32:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -71,11 +71,7 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 	vacuum_delay_point();
 
 	buffer = ReadBuffer(gv->index, blkno);
-
-	/*
-	 * This is only used during VACUUM FULL, so we need not bother to lock
-	 * individual index pages
-	 */
+	LockBuffer(buffer, GIST_EXCLUSIVE);
 	gistcheckpage(gv->index, buffer);
 	page = (Page) BufferGetPage(buffer);
 	maxoff = PageGetMaxOffsetNumber(page);
@@ -183,6 +179,11 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 				}
 				res.itup = vec;
 
+				for (ptr = dist; ptr; ptr = ptr->next)
+				{
+					MarkBufferDirty(ptr->buffer);
+				}
+
 				if (!gv->index->rd_istemp)
 				{
 					XLogRecPtr	recptr;
@@ -198,12 +199,10 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 					xlinfo = rdata->data;
 
 					recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_PAGE_SPLIT, rdata);
-					ptr = dist;
-					while (ptr)
+					for (ptr = dist; ptr; ptr = ptr->next)
 					{
 						PageSetLSN(BufferGetPage(ptr->buffer), recptr);
 						PageSetTLI(BufferGetPage(ptr->buffer), ThisTimeLineID);
-						ptr = ptr->next;
 					}
 
 					pfree(xlinfo);
@@ -211,21 +210,18 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 				}
 				else
 				{
-					ptr = dist;
-					while (ptr)
+					for (ptr = dist; ptr; ptr = ptr->next)
 					{
 						PageSetLSN(BufferGetPage(ptr->buffer), XLogRecPtrForTemp);
-						ptr = ptr->next;
 					}
 				}
 
-				ptr = dist;
-				while (ptr)
+				for (ptr = dist; ptr; ptr = ptr->next)
 				{
+					/* we must keep the buffer lock on the head page */
 					if (BufferGetBlockNumber(ptr->buffer) != blkno)
 						LockBuffer(ptr->buffer, GIST_UNLOCK);
-					WriteBuffer(ptr->buffer);
-					ptr = ptr->next;
+					ReleaseBuffer(ptr->buffer);
 				}
 
 				if (blkno == GIST_ROOT_BLKNO)
@@ -297,6 +293,8 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 
 	if (needwrite)
 	{
+		MarkBufferDirty(buffer);
+
 		if (!gv->index->rd_istemp)
 		{
 			XLogRecData *rdata;
@@ -317,13 +315,12 @@ gistVacuumUpdate(GistVacuum *gv, BlockNumber blkno, bool needunion)
 		}
 		else
 			PageSetLSN(page, XLogRecPtrForTemp);
-		WriteBuffer(buffer);
 	}
-	else
-		ReleaseBuffer(buffer);
 
 	END_CRIT_SECTION();
 
+	UnlockReleaseBuffer(buffer);
+
 	if (ncompleted && !gv->index->rd_istemp)
 		gistxlogInsertCompletion(gv->index->rd_node, completed, ncompleted);
 
@@ -429,8 +426,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS)
 		}
 		else
 			lastFilledBlock = blkno;
-		LockBuffer(buffer, GIST_UNLOCK);
-		ReleaseBuffer(buffer);
+		UnlockReleaseBuffer(buffer);
 	}
 	lastBlock = npages - 1;
 
@@ -569,8 +565,7 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 			if (stack->blkno == GIST_ROOT_BLKNO && !GistPageIsLeaf(page))
 			{
 				/* only the root can become non-leaf during relock */
-				LockBuffer(buffer, GIST_UNLOCK);
-				ReleaseBuffer(buffer);
+				UnlockReleaseBuffer(buffer);
 				/* one more check */
 				continue;
 			}
@@ -617,6 +612,8 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 			{
 				GistMarkTuplesDeleted(page);
 
+				MarkBufferDirty(buffer);
+
 				if (!rel->rd_istemp)
 				{
 					XLogRecData *rdata;
@@ -638,7 +635,6 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 				}
 				else
 					PageSetLSN(page, XLogRecPtrForTemp);
-				WriteNoReleaseBuffer(buffer);
 			}
 
 			END_CRIT_SECTION();
@@ -666,8 +662,7 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 			}
 		}
 
-		LockBuffer(buffer, GIST_UNLOCK);
-		ReleaseBuffer(buffer);
+		UnlockReleaseBuffer(buffer);
 
 		ptr = stack->next;
 		pfree(stack);