btrfs: move fs root init stuff into btrfs_init_fs_root

We have a helper for reading fs roots that just reads the fs root off
the disk and then sets REF_COWS and init's the inheritable flags.  Move
this into btrfs_init_fs_root so we can later get rid of this helper and
consolidate all of the fs root reading into one helper.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -1445,12 +1445,6 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
 	root = btrfs_read_tree_root(tree_root, location);
 	if (IS_ERR(root))
 		return root;
-
-	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
-		set_bit(BTRFS_ROOT_REF_COWS, &root->state);
-		btrfs_check_and_init_root_item(&root->root_item);
-	}
-
 	return root;
 }
 
@@ -1474,6 +1468,11 @@ int btrfs_init_fs_root(struct btrfs_root *root)
 	}
 	root->subv_writers = writers;
 
+	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
+		set_bit(BTRFS_ROOT_REF_COWS, &root->state);
+		btrfs_check_and_init_root_item(&root->root_item);
+	}
+
 	btrfs_init_free_ino_ctl(root);
 	spin_lock_init(&root->ino_cache_lock);
 	init_waitqueue_head(&root->ino_cache_wait);