diff options
| -rw-r--r-- | fs/btrfs/ctree.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index f1033448b667..5f7eea3fa1c6 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1431,10 +1431,30 @@ get_old_root(struct btrfs_root *root, u64 time_seq) "failed to read tree block %llu from get_old_root", logical); } else { + struct tree_mod_elem *tm2; + btrfs_tree_read_lock(old); eb = btrfs_clone_extent_buffer(old); + /* + * After the lookup for the most recent tree mod operation + * above and before we locked and cloned the extent buffer + * 'old', a new tree mod log operation may have been added. + * So lookup for a more recent one to make sure the number + * of mod log operations we replay is consistent with the + * number of items we have in the cloned extent buffer, + * otherwise we can hit a BUG_ON when rewinding the extent + * buffer. + */ + tm2 = tree_mod_log_search(fs_info, logical, time_seq); btrfs_tree_read_unlock(old); free_extent_buffer(old); + ASSERT(tm2); + ASSERT(tm2 == tm || tm2->seq > tm->seq); + if (!tm2 || tm2->seq < tm->seq) { + free_extent_buffer(eb); + return NULL; + } + tm = tm2; } } else if (old_root) { eb_root_owner = btrfs_header_owner(eb_root); |