From 199a7448c097514a029d29e666e3dbb3bdd01f92 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 3 Oct 2017 08:58:33 -0700
Subject: [PATCH] xfs: handle racy AIO in xfs_reflink_end_cow
References: bsc#1085535
Patch-mainline: v4.14-rc4
Git-commit: e12199f85d0ad1b04ce6c425ad93cd847fe930bb
Stable-commit: 199a7448c097514a029d29e666e3dbb3bdd01f92
commit e12199f85d0ad1b04ce6c425ad93cd847fe930bb upstream.
If we got two AIO writes into a COW area the second one might not have any
COW extents left to convert. Handle that case gracefully instead of
triggering an assert or accessing beyond the bounds of the extent list.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
---
fs/xfs/xfs_reflink.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index f45fbf0db9bb..8c8390a7f121 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -735,7 +735,13 @@ xfs_reflink_end_cow(
/* If there is a hole at end_fsb - 1 go to the previous extent */
if (!xfs_iext_lookup_extent(ip, ifp, end_fsb - 1, &idx, &got) ||
got.br_startoff > end_fsb) {
- ASSERT(idx > 0);
+ /*
+ * In case of racing, overlapping AIO writes no COW extents
+ * might be left by the time I/O completes for the loser of
+ * the race. In that case we are done.
+ */
+ if (idx <= 0)
+ goto out_cancel;
xfs_iext_get_extent(ifp, --idx, &got);
}
@@ -807,6 +813,7 @@ xfs_reflink_end_cow(
out_defer:
xfs_defer_cancel(&dfops);
+out_cancel:
xfs_trans_cancel(tp);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
out:
--
2.16.2