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, 13 insertions, 18 deletions

diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 2e1a4da38b..b270538bd8 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -31,7 +31,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.68 2006/03/05 15:58:25 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.69 2006/03/31 23:32:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -317,8 +317,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 				lazy_record_free_space(vacrelstats, blkno,
 									   PageGetFreeSpace(page));
 			}
-			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-			WriteBuffer(buf);
+			MarkBufferDirty(buf);
+			UnlockReleaseBuffer(buf);
 			continue;
 		}
 
@@ -327,8 +327,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 			empty_pages++;
 			lazy_record_free_space(vacrelstats, blkno,
 								   PageGetFreeSpace(page));
-			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-			ReleaseBuffer(buf);
+			UnlockReleaseBuffer(buf);
 			continue;
 		}
 
@@ -439,12 +438,9 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 		if (hastup)
 			vacrelstats->nonempty_pages = blkno + 1;
 
-		LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-
 		if (pgchanged)
-			WriteBuffer(buf);
-		else
-			ReleaseBuffer(buf);
+			MarkBufferDirty(buf);
+		UnlockReleaseBuffer(buf);
 	}
 
 	/* save stats for use later */
@@ -524,8 +520,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
 		page = BufferGetPage(buf);
 		lazy_record_free_space(vacrelstats, tblk,
 							   PageGetFreeSpace(page));
-		LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-		WriteBuffer(buf);
+		UnlockReleaseBuffer(buf);
 		npages++;
 	}
 
@@ -541,7 +536,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
  *	lazy_vacuum_page() -- free dead tuples on a page
  *					 and repair its fragmentation.
  *
- * Caller is expected to handle reading, locking, and writing the buffer.
+ * Caller must hold pin and lock on the buffer.
  *
  * tupindex is the index in vacrelstats->dead_tuples of the first dead
  * tuple for this page.  We assume the rest follow sequentially.
@@ -557,6 +552,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 	ItemId		itemid;
 
 	START_CRIT_SECTION();
+
 	for (; tupindex < vacrelstats->num_dead_tuples; tupindex++)
 	{
 		BlockNumber tblk;
@@ -572,6 +568,8 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 
 	uncnt = PageRepairFragmentation(page, unused);
 
+	MarkBufferDirty(buffer);
+
 	/* XLOG stuff */
 	if (!onerel->rd_istemp)
 	{
@@ -871,8 +869,7 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
 		if (PageIsNew(page) || PageIsEmpty(page))
 		{
 			/* PageIsNew probably shouldn't happen... */
-			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-			ReleaseBuffer(buf);
+			UnlockReleaseBuffer(buf);
 			continue;
 		}
 
@@ -928,9 +925,7 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
 			}
 		}						/* scan along page */
 
-		LockBuffer(buf, BUFFER_LOCK_UNLOCK);
-
-		ReleaseBuffer(buf);
+		UnlockReleaseBuffer(buf);
 
 		/* Done scanning if we found a tuple here */
 		if (hastup)