btrfs: fix invalid removal of root ref

[platform/kernel/linux-rpi.git] / fs / btrfs / inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 47fe2e8..6f0568f 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4260,13 +4260,16 @@ static int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
        }
        btrfs_release_path(path);
 
-       ret = btrfs_del_root_ref(trans, objectid, root->root_key.objectid,
-                                dir_ino, &index, name, name_len);
-       if (ret < 0) {
-               if (ret != -ENOENT) {
-                       btrfs_abort_transaction(trans, ret);
-                       goto out;
-               }
+       /*
+        * This is a placeholder inode for a subvolume we didn't have a
+        * reference to at the time of the snapshot creation.  In the meantime
+        * we could have renamed the real subvol link into our snapshot, so
+        * depending on btrfs_del_root_ref to return -ENOENT here is incorret.
+        * Instead simply lookup the dir_index_item for this entry so we can
+        * remove it.  Otherwise we know we have a ref to the root and we can
+        * call btrfs_del_root_ref, and it _shouldn't_ fail.
+        */
+       if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
                di = btrfs_search_dir_index_item(root, path, dir_ino,
                                                 name, name_len);
                if (IS_ERR_OR_NULL(di)) {
@@ -4281,8 +4284,16 @@ static int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                index = key.offset;
+               btrfs_release_path(path);
+       } else {
+               ret = btrfs_del_root_ref(trans, objectid,
+                                        root->root_key.objectid, dir_ino,
+                                        &index, name, name_len);
+               if (ret) {
+                       btrfs_abort_transaction(trans, ret);
+                       goto out;
+               }
        }
-       btrfs_release_path(path);
 
        ret = btrfs_delete_delayed_dir_index(trans, BTRFS_I(dir), index);
        if (ret) {