[PATCH v3 09/17] btrfs: release BG lock before calling btrfs_link_bg_list()

[Mark Harmstone <mark@harmstone.com>]

Release block_group->lock before calling btrfs_link_bg_list() in
btrfs_delete_unused_bgs(), as this was causing lockdep issues.

This lock isn't held in any other place that we call btrfs_link_bg_list(), as
the block group lists are manipulated while holding fs_info->unused_bgs_lock.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
Fixes: 0497dfba98c0 ("btrfs: codify pattern for adding block_group to bg_list")
---
 fs/btrfs/block-group.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index d3433a5b169f..a3c984f905fc 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1620,6 +1620,8 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		if ((space_info->total_bytes - block_group->length < used &&
 		     block_group->zone_unusable < block_group->length) ||
 		    has_unwritten_metadata(block_group)) {
+			spin_unlock(&block_group->lock);
+
 			/*
 			 * Add a reference for the list, compensate for the ref
 			 * drop under the "next" label for the
@@ -1628,7 +1630,6 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 			btrfs_link_bg_list(block_group, &retry_list);
 
 			trace_btrfs_skip_unused_block_group(block_group);
-			spin_unlock(&block_group->lock);
 			spin_unlock(&space_info->lock);
 			up_write(&space_info->groups_sem);
 			goto next;
-- 
2.49.1