On Mon, Mar 19, 2018 at 05:16:42PM +0900, Misono, Tomohiro wrote: > 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. Is there any way of adding a UUID to the top level subvol on an existing filesystem? It would be helpful not to have to rebuild every filesystem in the world to fix this. Hugo. > Signed-off-by: Tomohiro Misono <misono.tomohiro@xxxxxxxxxxxxxx> > --- > 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; -- Hugo Mills | This chap Anon is writing some perfectly lovely hugo@... carfax.org.uk | stuff at the moment. http://carfax.org.uk/ | PGP: E2AB1DE4 |
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