Btrfs: Add a write ahead tree log to optimize synchronous operations

File syncs and directory syncs are optimized by copying their
items into a special (copy-on-write) log tree.  There is one log tree per
subvolume and the btrfs super block points to a tree of log tree roots.

After a crash, items are copied out of the log tree and back into the
subvolume.  See tree-log.c for all the details.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 36726696e58b..e3984f902e71 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -202,8 +202,9 @@ again:
                 memcpy(&found_key, &key, sizeof(key));
                 key.offset++;
                 btrfs_release_path(root, path);
-                dead_root = btrfs_read_fs_root_no_radix(root->fs_info,
-                                                        &found_key);
+                dead_root =
+                        btrfs_read_fs_root_no_radix(root->fs_info->tree_root,
+                                                    &found_key);
                 if (IS_ERR(dead_root)) {
                         ret = PTR_ERR(dead_root);
                         goto err;