3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Jeff Mahoney <jeffm@xxxxxxxx> commit aa7c8da35d1905d80e840d075f07d26ec90144b5 upstream. In __btrfs_run_delayed_refs, the error path when run_delayed_extent_op fails sets locked_ref->processing = 0 but doesn't re-increment delayed_refs->num_heads_ready. As a result, we end up triggering the WARN_ON in btrfs_select_ref_head. Fixes: d7df2c796d7 (Btrfs: attach delayed ref updates to delayed ref heads) Reported-by: Jon Nelson <jnelson-suse@xxxxxxxxxxx> Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx> Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- fs/btrfs/extent-tree.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -2479,7 +2479,10 @@ static noinline int __btrfs_run_delayed_ */ if (must_insert_reserved) locked_ref->must_insert_reserved = 1; + spin_lock(&delayed_refs->lock); locked_ref->processing = 0; + delayed_refs->num_heads_ready++; + spin_unlock(&delayed_refs->lock); btrfs_debug(fs_info, "run_delayed_extent_op returned %d", ret); btrfs_delayed_ref_unlock(locked_ref); return ret;