diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
index 44ecb3c8c71..965a7d52541 100644
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Id: hio.c,v 1.43 2001/10/25 05:49:21 momjian Exp $
+ *	  $Id: hio.c,v 1.43.2.1 2005/05/07 21:34:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -245,13 +245,6 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	 */
 	buffer = ReadBuffer(relation, P_NEW);
 
-	/*
-	 * Release the file-extension lock; it's now OK for someone else to
-	 * extend the relation some more.
-	 */
-	if (!relation->rd_myxactonly)
-		UnlockPage(relation, 0, ExclusiveLock);
-
 	/*
 	 * We can be certain that locking the otherBuffer first is OK, since
 	 * it must have a lower page number.
@@ -260,9 +253,22 @@ RelationGetBufferForTuple(Relation relation, Size len,
 		LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
 
 	/*
-	 * We need to initialize the empty new page.
+	 * Now acquire lock on the new page.
 	 */
 	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+	/*
+	 * Release the file-extension lock; it's now OK for someone else to
+	 * extend the relation some more.  Note that we cannot release this
+	 * lock before we have buffer lock on the new page, or we risk a
+	 * race condition against vacuumlazy.c --- see comments therein.
+	 */
+	if (!relation->rd_myxactonly)
+		UnlockPage(relation, 0, ExclusiveLock);
+
+	/*
+	 * We need to initialize the empty new page.
+	 */
 	pageHeader = (Page) BufferGetPage(buffer);
 	Assert(PageIsNew((PageHeader) pageHeader));
 	PageInit(pageHeader, BufferGetPageSize(buffer), 0);
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 088ad9c8aed..c87e4192621 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -31,7 +31,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v 1.11 2002/01/06 00:37:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v 1.11.2.1 2005/05/07 21:34:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -259,8 +259,30 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 
 		if (PageIsNew(page))
 		{
-			/* Not sure we still need to handle this case, but... */
+			/*
+			 * An all-zeroes page could be left over if a backend extends
+			 * the relation but crashes before initializing the page.
+			 * Reclaim such pages for use.
+			 *
+			 * We have to be careful here because we could be looking at
+			 * a page that someone has just added to the relation and not
+			 * yet been able to initialize (see RelationGetBufferForTuple).
+			 * To interlock against that, release the buffer read lock
+			 * (which we must do anyway) and grab the relation extension
+			 * lock before re-locking in exclusive mode.  If the page is
+			 * still uninitialized by then, it must be left over from a
+			 * crashed backend, and we can initialize it.
+			 *
+			 * We don't really need the relation lock when this is a new
+			 * or temp relation, but it's probably not worth the code space
+			 * to check that, since this surely isn't a critical path.
+			 *
+			 * Note: the comparable code in vacuum.c need not do all this
+			 * because it's got exclusive lock on the whole relation.
+			 */
 			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
+			LockPage(onerel, 0, ExclusiveLock);
+			UnlockPage(onerel, 0, ExclusiveLock);
 			LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
 			if (PageIsNew(page))
 			{