Btrfs: fix locking issue in btrfs_remove_block_group

We should hold the block_group_cache_lock while modifying the
block groups red-black tree. Thank you,

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a4e36c3..3bed6a7 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5952,9 +5952,11 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
        path = btrfs_alloc_path();
        BUG_ON(!path);
 
-       btrfs_remove_free_space_cache(block_group);
+       spin_lock(&root->fs_info->block_group_cache_lock);
        rb_erase(&block_group->cache_node,
                 &root->fs_info->block_group_cache_tree);
+       spin_unlock(&root->fs_info->block_group_cache_lock);
+       btrfs_remove_free_space_cache(block_group);
        down_write(&block_group->space_info->groups_sem);
        list_del(&block_group->list);
        up_write(&block_group->space_info->groups_sem);