[PATCH] xfs: add missing error check in xfs_prepare_shift()

[Brian Foster <bfoster@redhat.com>]

xfs_prepare_shift() fails to check the error return from
xfs_flush_unmap_range(). If the latter fails, that could lead to an
insert/collapse range operation over a delalloc range, which is not
supported.

Add an error check and return appropriately. This is reproduced
rarely by generic/475.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_bmap_util.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 2db43ff4f8b5..06d07f1e310b 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1193,6 +1193,8 @@ xfs_prepare_shift(
 	 * about to shift down every extent from offset to EOF.
 	 */
 	error = xfs_flush_unmap_range(ip, offset, XFS_ISIZE(ip));
+	if (error)
+		return error;
 
 	/*
 	 * Clean out anything hanging around in the cow fork now that
-- 
2.17.2