xfs: remove incorrect log write optimization

We do need a barrier for the first buffer of a split log write. Otherwise we might incorrectly stamp the tail LSN into transactions in the first block, or not flush data I/O before updating the inode size.

Signed-off-by Christoph Hellwig <[email protected]>

Index: xfs-dev/fs/xfs/xfs_log.c
===================================================================

fs/xfs/xfs_log.c +2 -5

@@ -1423,11 +1423,8 @@ xlog_sync(xlog_t		*log,
 	XFS_BUF_BUSY(bp);
 	XFS_BUF_ASYNC(bp);
 	bp->b_flags |= XBF_LOG_BUFFER;
-	/*
-	 * Do an ordered write for the log block.
-	 * Its unnecessary to flush the first split block in the log wrap case.
-	 */
-	if (!split && (log->l_mp->m_flags & XFS_MOUNT_BARRIER))
+
+	if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
 		XFS_BUF_ORDERED(bp);
 
 	ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);

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We do need a barrier for the first buffer of a split log write. Otherwise we might incorrectly stamp the tail LSN into transactions in the first block, or not flush data I/O before updating the inode size.

Signed-off-by Christoph Hellwig <[email protected]>

Index: xfs-dev/fs/xfs/xfs_log.c
===================================================================

fs/xfs/xfs_log.c +2 -5

@@ -1423,11 +1423,8 @@ xlog_sync(xlog_t		*log,
 	XFS_BUF_BUSY(bp);
 	XFS_BUF_ASYNC(bp);
 	bp->b_flags |= XBF_LOG_BUFFER;
-	/*
-	 * Do an ordered write for the log block.
-	 * Its unnecessary to flush the first split block in the log wrap case.
-	 */
-	if (!split && (log->l_mp->m_flags & XFS_MOUNT_BARRIER))
+
+	if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
 		XFS_BUF_ORDERED(bp);
 
 	ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);

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http://oss.sgi.com/mailman/listinfo/xfs

Quoted 3 lines · Christoph Hellwig

We do need a barrier for the first buffer of a split log write. Otherwise we might incorrectly stamp the tail LSN into transactions in the first block, or not flush data I/O before updating the inode size.

I'm not sure whether "first block" means the one at the beginning of the log, or the one at the beginning of a split log write.

Quoted 5 lines · Alex Elder

Quoted 3 lines · Christoph Hellwig

We do need a barrier for the first buffer of a split log write. Otherwise we might incorrectly stamp the tail LSN into transactions in the first block, or not flush data I/O before updating the inode size.

Quoted 2 lines

I'm not sure whether "first block" means the one at the beginning of the log, or the one at the beginning of a split log write.

It means beginning of the split write. I can fix up the commit message if you want.