[PATCH v2] btrfs-progs: mkfs: add uuid and otime to ROOT_ITEM of, FS_TREE

[Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>]

Currently, the top-level subvolume lacks the UUID. As a result, both
non-snapshot subvolume and snapshot of top-level subvolume do not have
Parent UUID and cannot be distinguisued. Therefore "fi show" of
top-level lists all the subvolumes which lacks the UUID in
"Snapshot(s)" filed.  Also, it lacks the otime information.

Fix this by adding the UUID and otime at the mkfs time.  As a
consequence, snapshots of top-level subvolume now have a Parent UUID and
UUID tree will create an entry for top-level subvolume at mount time.
This should not cause the problem for current kernel, but user program
which relies on the empty Parent UUID may be affected by this change.

Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
---
v1 -> v2: clear o/ctime in create_tree()

 mkfs/common.c | 14 ++++++++++++++
 mkfs/main.c   |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/mkfs/common.c b/mkfs/common.c
index 16916ca2..6924d9b7 100644
--- a/mkfs/common.c
+++ b/mkfs/common.c
@@ -44,6 +44,7 @@ static int btrfs_create_tree_root(int fd, struct btrfs_mkfs_config *cfg,
 	u32 itemoff;
 	int ret = 0;
 	int blk;
+	u8 uuid[BTRFS_UUID_SIZE];
 
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
@@ -77,6 +78,19 @@ static int btrfs_create_tree_root(int fd, struct btrfs_mkfs_config *cfg,
 		btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
 		btrfs_set_item_size(buf, btrfs_item_nr(nritems),
 				sizeof(root_item));
+		if (blk == MKFS_FS_TREE) {
+			time_t now = time(NULL);
+
+			uuid_generate(uuid);
+			memcpy(root_item.uuid, uuid, BTRFS_UUID_SIZE);
+			btrfs_set_stack_timespec_sec(&root_item.otime, now);
+			btrfs_set_stack_timespec_sec(&root_item.ctime, now);
+		} else {
+			memset(uuid, 0, BTRFS_UUID_SIZE);
+			memcpy(root_item.uuid, uuid, BTRFS_UUID_SIZE);
+			btrfs_set_stack_timespec_sec(&root_item.otime, 0);
+			btrfs_set_stack_timespec_sec(&root_item.ctime, 0);
+		}
 		write_extent_buffer(buf, &root_item,
 			btrfs_item_ptr_offset(buf, nritems),
 			sizeof(root_item));
diff --git a/mkfs/main.c b/mkfs/main.c
index 5a717f70..40efa26b 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -315,6 +315,7 @@ static int create_tree(struct btrfs_trans_handle *trans,
 	struct btrfs_key location;
 	struct btrfs_root_item root_item;
 	struct extent_buffer *tmp;
+	u8 uuid[BTRFS_UUID_SIZE] = {0};
 	int ret;
 
 	ret = btrfs_copy_root(trans, root, root->node, &tmp, objectid);
@@ -325,6 +326,10 @@ static int create_tree(struct btrfs_trans_handle *trans,
 	btrfs_set_root_bytenr(&root_item, tmp->start);
 	btrfs_set_root_level(&root_item, btrfs_header_level(tmp));
 	btrfs_set_root_generation(&root_item, trans->transid);
+	/* clear uuid and o/ctime of source tree */
+	memcpy(root_item.uuid, uuid, BTRFS_UUID_SIZE);
+	btrfs_set_stack_timespec_sec(&root_item.otime, 0);
+	btrfs_set_stack_timespec_sec(&root_item.ctime, 0);
 	free_extent_buffer(tmp);
 
 	location.objectid = objectid;
-- 
2.14.3