Btrfs: fix sleep with spinlock held during unmount

The code to free block groups needs to drop the space info spin lock
before calling btrfs_remove_free_space_cache (which can schedule).

This is safe because at unmount time, nobody else is going to play
with the block groups.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5258923d621f..fe4e11b31a43 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3157,9 +3157,13 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
                 block_group = rb_entry(n, struct btrfs_block_group_cache,
                                        cache_node);
 
+                spin_unlock(&info->block_group_cache_lock);
                 btrfs_remove_free_space_cache(block_group);
+                spin_lock(&info->block_group_cache_lock);
+
                 rb_erase(&block_group->cache_node,
                          &info->block_group_cache_tree);
+
                 spin_lock(&block_group->space_info->lock);
                 list_del(&block_group->list);
                 spin_unlock(&block_group->space_info->lock);