Patch "xfs: clear delalloc and cache on buffered write failure" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

xfs: clear delalloc and cache on buffered write failure

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xfs-clear-delalloc-and-cache-on-buffered-write-failure.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Brian Foster <[email protected]>
Date: Thu, 16 Feb 2017 17:19:12 -0800
Subject: xfs: clear delalloc and cache on buffered write failure

From: Brian Foster <[email protected]>

commit fa7f138ac4c70dc00519c124cf7cd4862a0a5b0e upstream.

The buffered write failure handling code in xfs_file_iomap_end_delalloc() has a couple minor problems. First, if written == 0, start_fsb is not rounded down and it fails to kill off a delalloc block if the start offset is block unaligned. This results in a lingering delalloc block and broken delalloc block accounting detected at unmount time. Fix this by rounding down start_fsb in the unlikely event that written == 0.

Second, it is possible for a failed overwrite of a delalloc extent to leave dirty pagecache around over a hole in the file. This is because is possible to hit ->iomap_end() on write failure before the iomap code has attempted to allocate pagecache, and thus has no need to clean it up. If the targeted delalloc extent was successfully written by a previous write, however, then it does still have dirty pages when ->iomap_end() punches out the underlying blocks. This ultimately results in writeback over a hole. To fix this problem, unconditionally punch out the pagecache from XFS before the associated delalloc range.

---
 fs/xfs/xfs_iomap.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

@@ -1102,7 +1102,15 @@ xfs_file_iomap_end_delalloc(
 	xfs_fileoff_t		end_fsb;
 	int			error = 0;
 
-	start_fsb = XFS_B_TO_FSB(mp, offset + written);
+	/*
+	 * start_fsb refers to the first unused block after a short write. If
+	 * nothing was written, round offset down to point at the first block in
+	 * the range.
+	 */
+	if (unlikely(!written))
+		start_fsb = XFS_B_TO_FSBT(mp, offset);
+	else
+		start_fsb = XFS_B_TO_FSB(mp, offset + written);
 	end_fsb = XFS_B_TO_FSB(mp, offset + length);
 
 	/*

@@ -1114,6 +1122,9 @@ xfs_file_iomap_end_delalloc(
 	 * blocks in the range, they are ours.
 	 */
 	if (start_fsb < end_fsb) {
+		truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
+					 XFS_FSB_TO_B(mp, end_fsb) - 1);
+
 		xfs_ilock(ip, XFS_ILOCK_EXCL);
 		error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
 					       end_fsb - start_fsb);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/xfs-clear-delalloc-and-cache-on-buffered-write-failure.patch