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.tomoh...@jp.fujitsu.com> --- This is also needed in order that "sub list -s" works properly for non-privileged user[1] even if there are snapshots of toplevel subvolume. Currently the check if a subvolume is a snapshot is done by looking at the key offset of ROOT_ITEM of subvolume (non-zero for snapshot) used by tree search ioctl. However, non-privileged version of "sub list" won't use tree search ioctl and just looking if parent uuid is null or not. Therefore there is no way to recognize snapshots of toplevel subvolume. [1] https://marc.info/?l=linux-btrfs&m=152144463907830&w=2 mkfs/common.c | 14 ++++++++++++++ mkfs/main.c | 3 +++ 2 files changed, 17 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..52d92581 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 +326,8 @@ 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 of source tree */ + memcpy(root_item.uuid, uuid, BTRFS_UUID_SIZE); free_extent_buffer(tmp); location.objectid = objectid; -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
