Btrfs: set UUID in root_item for created trees

It is a rare exception that a new tree is created, like the qgroups
tree. So far these new trees have an all-zero UUID in their root
items. All trees that mkfs.btrfs has created get an UUID during the
first mount when btrfs_read_root_item() rewrites the root_item to
the v2 structure style. These UUID are never used so far, but
anyway, since it is better to have it uniform for all trees, this
commit adds some lines that generate and write an UUID for newly
created trees.

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

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a03a966505484d37beb1a9be81f72ad52f9de1a4..e4488b57a7aef1e435a57cc2bbb4ca28e2665f82 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -30,6 +30,7 @@
 #include <linux/slab.h>
 #include <linux/migrate.h>
 #include <linux/ratelimit.h>
+#include <linux/uuid.h>
 #include <asm/unaligned.h>
 #include "compat.h"
 #include "ctree.h"
@@ -1280,6 +1281,7 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
        struct btrfs_key key;
        int ret = 0;
        u64 bytenr;
+       uuid_le uuid;
 
        root = btrfs_alloc_root(fs_info);
        if (!root)
@@ -1329,6 +1331,8 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
        btrfs_set_root_used(&root->root_item, leaf->len);
        btrfs_set_root_last_snapshot(&root->root_item, 0);
        btrfs_set_root_dirid(&root->root_item, 0);
+       uuid_le_gen(&uuid);
+       memcpy(root->root_item.uuid, uuid.b, BTRFS_UUID_SIZE);
        root->root_item.drop_level = 0;
 
        key.objectid = objectid;