1 files changed, 15 insertions, 13 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 15cbc2bf4ff0..7d1e4fc5fb6a 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1024,11 +1024,18 @@ __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
                 if (!looped && !tm)
                         return 0;
                 /*
-                 * we must have key remove operations in the log before the
-                 * replace operation.
+                 * if there are no tree operation for the oldest root, we simply
+                 * return it. this should only happen if that (old) root is at
+                 * level 0.
                  */
-                BUG_ON(!tm);
+                if (!tm)
+                        break;
 
+                /*
+                 * if there's an operation that's not a root replacement, we
+                 * found the oldest version of our root. normally, we'll find a
+                 * MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
+                 */
                 if (tm->op != MOD_LOG_ROOT_REPLACE)
                         break;
 
@@ -1192,16 +1199,8 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
         }
 
         tm = tree_mod_log_search(root->fs_info, logical, time_seq);
-        /*
-         * there was an item in the log when __tree_mod_log_oldest_root
-         * returned. this one must not go away, because the time_seq passed to
-         * us must be blocking its removal.
-         */
-        BUG_ON(!tm);
-
         if (old_root)
-                eb = alloc_dummy_extent_buffer(tm->index << PAGE_CACHE_SHIFT,
-                                               root->nodesize);
+                eb = alloc_dummy_extent_buffer(logical, root->nodesize);
         else
                 eb = btrfs_clone_extent_buffer(root->node);
         btrfs_tree_read_unlock(root->node);
@@ -1216,7 +1215,10 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
                 btrfs_set_header_level(eb, old_root->level);
                 btrfs_set_header_generation(eb, old_generation);
         }
-        __tree_mod_log_rewind(eb, time_seq, tm);
+        if (tm)
+                __tree_mod_log_rewind(eb, time_seq, tm);
+        else
+                WARN_ON(btrfs_header_level(eb) != 0);
         extent_buffer_get(eb);
 
         return eb;