From 5403a7851823fd2686a3f29d12208414eb6dd1b0 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki@enterprisedb.com>
Date: Tue, 20 Jan 2009 18:59:37 +0000
Subject: [PATCH] Add a new option to RestoreBkpBlocks() to indicate if a
 cleanup lock should be used instead of the normal exclusive lock, and make
 WAL redo functions responsible for calling RestoreBkpBlocks(). They know
 better what kind of a lock they need.

At the moment, this just moves things around with no functional change, but
makes the hot standby patch that's under review cleaner.
---
 src/backend/access/gin/ginxlog.c          |  2 ++
 src/backend/access/gist/gistxlog.c        |  3 +-
 src/backend/access/heap/heapam.c          |  5 +++
 src/backend/access/nbtree/nbtxlog.c       |  2 ++
 src/backend/access/transam/clog.c         |  3 ++
 src/backend/access/transam/multixact.c    |  3 ++
 src/backend/access/transam/xact.c         |  3 ++
 src/backend/access/transam/xlog.c         | 21 ++++++++---
 src/backend/access/transam/xlogutils.c    | 43 +++++++++++++++--------
 src/backend/catalog/storage.c             |  3 ++
 src/backend/commands/dbcommands.c         |  3 ++
 src/backend/commands/sequence.c           |  3 ++
 src/backend/commands/tablespace.c         |  3 ++
 src/backend/storage/freespace/freespace.c |  2 ++
 src/include/access/xlog.h                 |  2 ++
 15 files changed, 80 insertions(+), 21 deletions(-)

diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index d2cff392e5..8382576d3c 100644
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -438,6 +438,8 @@ gin_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	RestoreBkpBlocks(lsn, record, false);
+
 	topCtx = MemoryContextSwitchTo(opCtx);
 	switch (info)
 	{
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index 116449e3c8..4a20d905d4 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -394,9 +394,10 @@ void
 gist_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
-
 	MemoryContext oldCxt;
 
+	RestoreBkpBlocks(lsn, record, false);
+
 	oldCxt = MemoryContextSwitchTo(opCtx);
 	switch (info)
 	{
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 4af17c8079..52115cf64e 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -4777,6 +4777,8 @@ heap_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	RestoreBkpBlocks(lsn, record, false);
+
 	switch (info & XLOG_HEAP_OPMASK)
 	{
 		case XLOG_HEAP_INSERT:
@@ -4816,12 +4818,15 @@ heap2_redo(XLogRecPtr lsn, XLogRecord *record)
 	switch (info & XLOG_HEAP_OPMASK)
 	{
 		case XLOG_HEAP2_FREEZE:
+			RestoreBkpBlocks(lsn, record, false);
 			heap_xlog_freeze(lsn, record);
 			break;
 		case XLOG_HEAP2_CLEAN:
+			RestoreBkpBlocks(lsn, record, true);
 			heap_xlog_clean(lsn, record, false);
 			break;
 		case XLOG_HEAP2_CLEAN_MOVE:
+			RestoreBkpBlocks(lsn, record, true);
 			heap_xlog_clean(lsn, record, true);
 			break;
 		default:
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index a874e491f5..517c4b90ce 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -714,6 +714,8 @@ btree_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	RestoreBkpBlocks(lsn, record, false);
+
 	switch (info)
 	{
 		case XLOG_BTREE_INSERT_LEAF:
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index c80867c472..528a219db4 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -684,6 +684,9 @@ clog_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in clog records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == CLOG_ZEROPAGE)
 	{
 		int			pageno;
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 78d47154c9..7314341101 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1870,6 +1870,9 @@ multixact_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in multixact records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_MULTIXACT_ZERO_OFF_PAGE)
 	{
 		int			pageno;
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 23f6ea0a8b..c94e2a2251 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -4308,6 +4308,9 @@ xact_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in xact records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_XACT_COMMIT)
 	{
 		xl_xact_commit *xlrec = (xl_xact_commit *) XLogRecGetData(record);
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 7debb34072..bd6035d4a6 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2922,9 +2922,15 @@ CleanupBackupHistory(void)
  * page might not be.  This will force us to replay all subsequent
  * modifications of the page that appear in XLOG, rather than possibly
  * ignoring them as already applied, but that's not a huge drawback.
+ *
+ * If 'cleanup' is true, a cleanup lock is used when restoring blocks.
+ * Otherwise, a normal exclusive lock is used.  At the moment, that's just
+ * pro forma, because there can't be any regular backends in the system
+ * during recovery.  The 'cleanup' argument applies to all backup blocks
+ * in the WAL record, that suffices for now.
  */
-static void
-RestoreBkpBlocks(XLogRecord *record, XLogRecPtr lsn)
+void
+RestoreBkpBlocks(XLogRecPtr lsn, XLogRecord *record, bool cleanup)
 {
 	Buffer		buffer;
 	Page		page;
@@ -2944,6 +2950,11 @@ RestoreBkpBlocks(XLogRecord *record, XLogRecPtr lsn)
 		buffer = XLogReadBufferExtended(bkpb.node, bkpb.fork, bkpb.block,
 										RBM_ZERO);
 		Assert(BufferIsValid(buffer));
+		if (cleanup)
+			LockBufferForCleanup(buffer);
+		else
+			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
 		page = (Page) BufferGetPage(buffer);
 
 		if (bkpb.hole_length == 0)
@@ -5199,9 +5210,6 @@ StartupXLOG(void)
 					TransactionIdAdvance(ShmemVariableCache->nextXid);
 				}
 
-				if (record->xl_info & XLR_BKP_BLOCK_MASK)
-					RestoreBkpBlocks(record, EndRecPtr);
-
 				RmgrTable[record->xl_rmid].rm_redo(EndRecPtr, record);
 
 				/* Pop the error context stack */
@@ -6233,6 +6241,9 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in xlog records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_NEXTOID)
 	{
 		Oid			nextOid;
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index ef5fe4cef7..4a86271019 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -217,8 +217,19 @@ XLogCheckInvalidPages(void)
 
 /*
  * XLogReadBuffer
- *		A shorthand of XLogReadBufferExtended(), for reading from the main
- *		fork.
+ *		Read a page during XLOG replay.
+ *
+ * This is a shorthand of XLogReadBufferExtended() followed by
+ * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), for reading from the main
+ * fork.
+ *
+ * (Getting the lock is not really necessary, since we expect that this is
+ * only used during single-process XLOG replay, but some subroutines such
+ * as MarkBufferDirty will complain if we don't. And hopefully we'll get
+ * hot standby support in the future, where there will be backends running
+ * read-only queries during XLOG replay.)
+ *
+ * The returned buffer is exclusively-locked.
  *
  * For historical reasons, instead of a ReadBufferMode argument, this only
  * supports RBM_ZERO (init == true) and RBM_NORMAL (init == false) modes.
@@ -226,22 +237,21 @@ XLogCheckInvalidPages(void)
 Buffer
 XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
 {
-	return XLogReadBufferExtended(rnode, MAIN_FORKNUM, blkno,
-								  init ? RBM_ZERO : RBM_NORMAL);
+	Buffer buf;
+	buf = XLogReadBufferExtended(rnode, MAIN_FORKNUM, blkno,
+								 init ? RBM_ZERO : RBM_NORMAL);
+	if (BufferIsValid(buf))
+		LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+
+	return buf;
 }
 
 /*
  * XLogReadBufferExtended
  *		Read a page during XLOG replay
  *
- * This is functionally comparable to ReadBuffer followed by
- * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE): you get back a pinned
- * and locked buffer.  (Getting the lock is not really necessary, since we
- * expect that this is only used during single-process XLOG replay, but
- * some subroutines such as MarkBufferDirty will complain if we don't.)
- *
- * There's some differences in the behavior wrt. the "mode" argument,
- * compared to ReadBufferExtended:
+ * This is functionally comparable to ReadBufferExtended. There's some
+ * differences in the behavior wrt. the "mode" argument:
  *
  * 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
@@ -306,16 +316,19 @@ XLogReadBufferExtended(RelFileNode rnode, ForkNumber forknum,
 		Assert(BufferGetBlockNumber(buffer) == blkno);
 	}
 
-	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
-
 	if (mode == RBM_NORMAL)
 	{
 		/* check that page has been initialized */
 		Page		page = (Page) BufferGetPage(buffer);
 
+		/*
+		 * We assume that PageIsNew is safe without a lock. During recovery,
+		 * there should be no other backends that could modify the buffer at
+		 * the same time.
+		 */
 		if (PageIsNew(page))
 		{
-			UnlockReleaseBuffer(buffer);
+			ReleaseBuffer(buffer);
 			log_invalid_page(rnode, forknum, blkno, true);
 			return InvalidBuffer;
 		}
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index e9008e3f2c..309fa469ad 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -401,6 +401,9 @@ smgr_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in smgr records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_SMGR_CREATE)
 	{
 		xl_smgr_create *xlrec = (xl_smgr_create *) XLogRecGetData(record);
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 50cb6780d5..7e065762a8 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -1941,6 +1941,9 @@ dbase_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in dbase records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_DBASE_CREATE)
 	{
 		xl_dbase_create_rec *xlrec = (xl_dbase_create_rec *) XLogRecGetData(record);
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index c80f2a669a..46d7683377 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -1339,6 +1339,9 @@ seq_redo(XLogRecPtr lsn, XLogRecord *record)
 	xl_seq_rec *xlrec = (xl_seq_rec *) XLogRecGetData(record);
 	sequence_magic *sm;
 
+	/* Backup blocks are not used in seq records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info != XLOG_SEQ_LOG)
 		elog(PANIC, "seq_redo: unknown op code %u", info);
 
diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 7fa4bfba62..ee0c6428ef 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -1276,6 +1276,9 @@ tblspc_redo(XLogRecPtr lsn, XLogRecord *record)
 {
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
+	/* Backup blocks are not used in tblspc records */
+	Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
+
 	if (info == XLOG_TBLSPC_CREATE)
 	{
 		xl_tblspc_create_rec *xlrec = (xl_tblspc_create_rec *) XLogRecGetData(record);
diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c
index 8ef11be652..7fcd51e638 100644
--- a/src/backend/storage/freespace/freespace.c
+++ b/src/backend/storage/freespace/freespace.c
@@ -212,6 +212,8 @@ XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
 
 	/* If the page doesn't exist already, extend */
 	buf = XLogReadBufferExtended(rnode, FSM_FORKNUM, blkno, RBM_ZERO_ON_ERROR);
+	LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+
 	page = BufferGetPage(buf);
 	if (PageIsNew(page))
 		PageInit(page, BLCKSZ, 0);
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 5b7374ee66..6913f7c800 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -194,6 +194,8 @@ extern bool XLogNeedsFlush(XLogRecPtr RecPtr);
 
 extern void XLogSetAsyncCommitLSN(XLogRecPtr record);
 
+extern void RestoreBkpBlocks(XLogRecPtr lsn, XLogRecord *record, bool cleanup);
+
 extern void xlog_redo(XLogRecPtr lsn, XLogRecord *record);
 extern void xlog_desc(StringInfo buf, uint8 xl_info, char *rec);
 
-- 
2.39.5