Btrfs: create UUID tree if required

This tree is not created by mkfs.btrfs. Therefore when a filesystem
is mounted writable and the UUID tree does not exist, this tree is
created if required. The tree is also added to the fs_info structure
and initialized, but this commit does not yet read or write UUID tree
elements.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 306547b51a13..e084218c09d2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3429,6 +3429,32 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
 	return 0;
 }
 
+int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *tree_root = fs_info->tree_root;
+	struct btrfs_root *uuid_root;
+
+	/*
+	 * 1 - root node
+	 * 1 - root item
+	 */
+	trans = btrfs_start_transaction(tree_root, 2);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	uuid_root = btrfs_create_tree(trans, fs_info,
+				      BTRFS_UUID_TREE_OBJECTID);
+	if (IS_ERR(uuid_root)) {
+		btrfs_abort_transaction(trans, tree_root,
+					PTR_ERR(uuid_root));
+		return PTR_ERR(uuid_root);
+	}
+
+	fs_info->uuid_root = uuid_root;
+
+	return btrfs_commit_transaction(trans, tree_root);
+}
 /*
  * shrinking a device means finding all of the device extents past
  * the new size, and then following the back refs to the chunks.