[PATCH 3.16 186/410] Btrfs: fix deadlock in run_delalloc_nocow

[Ben Hutchings]

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Liu Bo <bo.li....@oracle.com>

commit e89166990f11c3f21e1649d760dd35f9e410321c upstream.

@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.

Signed-off-by: Liu Bo <bo.li....@oracle.com>
Reviewed-by: Josef Bacik <jba...@fb.com>
Signed-off-by: David Sterba <dste...@suse.com>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 fs/btrfs/inode.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1235,8 +1235,11 @@ next_slot:
                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];