Btrfs: use down_read_nested to make lockdep silent
authorLiu Bo <bo.li.liu@oracle.com>
Thu, 1 Dec 2016 00:11:04 +0000 (16:11 -0800)
committerDavid Sterba <dsterba@suse.com>
Tue, 3 Jan 2017 14:19:17 +0000 (15:19 +0100)
commite321f8a801d7b4c40da8005257b05b9c2b51b072
tree11df9f784d72ca301b9bfca794fe70c9a0c43628
parentd0280996437081dd12ed1e982ac8aeaa62835ec4
Btrfs: use down_read_nested to make lockdep silent

If @block_group is not @used_bg, it'll try to get @used_bg's lock without
droping @block_group 's lock and lockdep has throwed a scary deadlock warning
about it.
Fix it by using down_read_nested.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/extent-tree.c