Unite ReadBufferWithFork, ReadBufferWithStrategy, and ZeroOrReadBuffer

functions into one ReadBufferExtended function, that takes the strategy
and mode as argument. There's three modes, RBM_NORMAL which is the default
used by plain ReadBuffer(), RBM_ZERO, which replaces ZeroOrReadBuffer, and
a new mode RBM_ZERO_ON_ERROR, which allows callers to read corrupt pages
without throwing an error. The FSM needs the new mode to recover from
corrupt pages, which could happend if we crash after extending an FSM file,
and the new page is "torn".

Add fork number to some error messages in bufmgr.c, that still lacked it.

1 files changed, 32 insertions, 30 deletions

diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index 9abcce65483..5e60d6cccd1 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.59 2008/09/30 10:52:11 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.60 2008/10/31 15:04:59 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -200,6 +200,20 @@ XLogCheckInvalidPages(void)
 	invalid_page_tab = NULL;
 }
 
+/*
+ * XLogReadBufferExtended
+ *		A shorthand of XLogReadBufferExtended(), for reading from the main
+ *		fork.
+ *
+ * For historical reasons, instead of a ReadBufferMode argument, this only
+ * supports RBM_ZERO (init == true) and RBM_NORMAL (init == false) modes.
+ */
+Buffer
+XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
+{
+	return XLogReadBufferExtended(rnode, MAIN_FORKNUM, blkno,
+								  init ? RBM_ZERO : RBM_NORMAL);
+}
 
 /*
  * XLogReadBuffer
@@ -211,34 +225,21 @@ XLogCheckInvalidPages(void)
  * expect that this is only used during single-process XLOG replay, but
  * some subroutines such as MarkBufferDirty will complain if we don't.)
  *
- * If "init" is true then the caller intends to rewrite the page fully
- * using the info in the XLOG record.  In this case we will extend the
- * relation if needed to make the page exist, and we will not complain about
- * the page being "new" (all zeroes); in fact, we usually will supply a
- * zeroed buffer without reading the page at all, so as to avoid unnecessary
- * failure if the page is present on disk but has corrupt headers.
+ * There's some differences in the behavior wrt. the "mode" argument,
+ * compared to ReadBufferExtended:
  *
- * If "init" is false then the caller needs the page to be valid already.
- * If the page doesn't exist or contains zeroes, we return InvalidBuffer.
- * In this case the caller should silently skip the update on this page.
- * (In this situation, we expect that the page was later dropped or truncated.
- * If we don't see evidence of that later in the WAL sequence, we'll complain
- * at the end of WAL replay.)
- */
-Buffer
-XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
-{
-	return XLogReadBufferWithFork(rnode, MAIN_FORKNUM, blkno, init);
-}
-
-/*
- * XLogReadBufferWithFork
- *		Like XLogReadBuffer, but for reading other relation forks than
- *		the main one.
+ * In RBM_NORMAL mode, if the page doesn't exist, or contains all-zeroes, we
+ * return InvalidBuffer. In this case the caller should silently skip the
+ * update on this page. (In this situation, we expect that the page was later
+ * dropped or truncated. If we don't see evidence of that later in the WAL
+ * sequence, we'll complain at the end of WAL replay.)
+ *
+ * In RBM_ZERO and RBM_ZERO_ON_ERROR modes, if the page doesn't exist, the
+ * relation is extended with all-zeroes pages up to the given block number.
  */
 Buffer
-XLogReadBufferWithFork(RelFileNode rnode, ForkNumber forknum,
-					   BlockNumber blkno, bool init)
+XLogReadBufferExtended(RelFileNode rnode, ForkNumber forknum,
+					   BlockNumber blkno, ReadBufferMode mode)
 {
 	BlockNumber lastblock;
 	Buffer		buffer;
@@ -264,12 +265,13 @@ XLogReadBufferWithFork(RelFileNode rnode, ForkNumber forknum,
 	if (blkno < lastblock)
 	{
 		/* page exists in file */
-		buffer = ReadBufferWithoutRelcache(rnode, false, forknum, blkno, init);
+		buffer = ReadBufferWithoutRelcache(rnode, false, forknum, blkno,
+										   mode, NULL);
 	}
 	else
 	{
 		/* hm, page doesn't exist in file */
-		if (!init)
+		if (mode == RBM_NORMAL)
 		{
 			log_invalid_page(rnode, forknum, blkno, false);
 			return InvalidBuffer;
@@ -283,7 +285,7 @@ XLogReadBufferWithFork(RelFileNode rnode, ForkNumber forknum,
 			if (buffer != InvalidBuffer)
 				ReleaseBuffer(buffer);
 			buffer = ReadBufferWithoutRelcache(rnode, false, forknum,
-											   P_NEW, false);
+											   P_NEW, mode, NULL);
 			lastblock++;
 		}
 		Assert(BufferGetBlockNumber(buffer) == blkno);
@@ -291,7 +293,7 @@ XLogReadBufferWithFork(RelFileNode rnode, ForkNumber forknum,
 
 	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
 
-	if (!init)
+	if (mode == RBM_NORMAL)
 	{
 		/* check that page has been initialized */
 		Page		page = (Page) BufferGetPage(buffer);