From: Liu Bo <bo.li.liu@oracle.com>
Date: Thu, 25 Jan 2018 11:02:50 -0700
Subject: Btrfs: fix deadlock in run_delalloc_nocow
Git-commit: e89166990f11c3f21e1649d760dd35f9e410321c
Patch-mainline: v4.16-rc2
References: bsc#1083000

@cur_offset is not set back to what it should be (@cow_start) if
btrfs_next_leaf() returns something wrong, and the range [cow_start,
cur_offset) remains locked forever.

cc: <stable@vger.kernel.org>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/inode.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c5f31817778b..a68a4acd16e5 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1334,8 +1334,11 @@ static noinline int run_delalloc_nocow(struct inode *inode,
 		leaf = path->nodes[0];
 		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
+			if (ret < 0) {
+				if (cow_start != (u64)-1)
+					cur_offset = cow_start;
 				goto error;
+			}
 			if (ret > 0)
 				break;
 			leaf = path->nodes[0];