Btrfs: determine level of old roots

In btrfs_find_all_roots' termination condition, we compare the level of the
old buffer we got from btrfs_search_old_slot to the level of the current
root node. We'd better compare it to the level of the rewinded root node.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

3 files changed, 19 insertions, 3 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index f3187938e081..65608fbf2232 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -283,9 +283,7 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
                 goto out;
         }
 
-        rcu_read_lock();
-        root_level = btrfs_header_level(root->node);
-        rcu_read_unlock();
+        root_level = btrfs_old_root_level(root, time_seq);
 
         if (root_level + 1 == level)
                 goto out;
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index d9308c38a8f2..ef68c33eefd9 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1297,6 +1297,23 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
         return eb;
 }
 
+int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
+{
+        struct tree_mod_elem *tm;
+        int level;
+
+        tm = __tree_mod_log_oldest_root(root->fs_info, root, time_seq);
+        if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
+                level = tm->old_root.level;
+        } else {
+                rcu_read_lock();
+                level = btrfs_header_level(root->node);
+                rcu_read_unlock();
+        }
+
+        return level;
+}
+
 static inline int should_cow_block(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root,
                                    struct extent_buffer *buf)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1630be831210..34c5a442dd33 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3120,6 +3120,7 @@ static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
 {
         return atomic_inc_return(&fs_info->tree_mod_seq);
 }
+int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq);
 
 /* root-item.c */
 int btrfs_find_root_ref(struct btrfs_root *tree_root,