Btrfs: Add properly locking around add_root_to_dirty_list

add_root_to_dirty_list happens once at the very beginning of the
transaction, but it is still racey.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index e801f226d7e0..086303b9be64 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -220,10 +220,12 @@ struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
  */
 static void add_root_to_dirty_list(struct btrfs_root *root)
 {
+        spin_lock(&root->fs_info->trans_lock);
         if (root->track_dirty && list_empty(&root->dirty_list)) {
                 list_add(&root->dirty_list,
                          &root->fs_info->dirty_cowonly_roots);
         }
+        spin_unlock(&root->fs_info->trans_lock);
 }
 
 /*