1 files changed, 12 insertions, 1 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 15384968a84a..10ae5700ab1e 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -301,23 +301,34 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
         int ret = 0;
         int root_level;
         int level = ref->level;
+        int index;
 
         root_key.objectid = ref->root_id;
         root_key.type = BTRFS_ROOT_ITEM_KEY;
         root_key.offset = (u64)-1;
+
+        index = srcu_read_lock(&fs_info->subvol_srcu);
+
         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
         if (IS_ERR(root)) {
+                srcu_read_unlock(&fs_info->subvol_srcu, index);
                 ret = PTR_ERR(root);
                 goto out;
         }
 
         root_level = btrfs_old_root_level(root, time_seq);
 
-        if (root_level + 1 == level)
+        if (root_level + 1 == level) {
+                srcu_read_unlock(&fs_info->subvol_srcu, index);
                 goto out;
+        }
 
         path->lowest_level = level;
         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
+
+        /* root node has been locked, we can release @subvol_srcu safely here */
+        srcu_read_unlock(&fs_info->subvol_srcu, index);
+
         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
                  "%d for key (%llu %u %llu)\n",
                  ref->root_id, level, ref->count, ret,