Btrfs: introduce subvol uuids and times

This patch introduces uuids for subvolumes. Each
subvolume has it's own uuid. In case it was snapshotted,
it also contains parent_uuid. In case it was received,
it also contains received_uuid.

It also introduces subvolume ctime/otime/stime/rtime. The
first two are comparable to the times found in inodes. otime
is the origin/creation time and ctime is the change time.
stime/rtime are only valid on received subvolumes.
stime is the time of the subvolume when it was
sent. rtime is the time of the subvolume when it was
received.

Additionally to the times, we have a transid for each
time. They are updated at the same place as the times.

btrfs receive uses stransid and rtransid to find out
if a received subvolume changed in the meantime.

If an older kernel mounts a filesystem with the
extented fields, all fields become invalid. The next
mount with a new kernel will detect this and reset the
fields.

Signed-off-by: Alexander Block <ablock84@googlemail.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Reviewed-by: Arne Jansen <sensille@gmx.net>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Reviewed-by: Alex Lyakas <alex.bolshoy.btrfs@gmail.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index da6e9364a5e..9197e2e3340 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -1032,6 +1032,7 @@ continue_with_current_leaf_stack_frame:
 			struct btrfs_disk_key *disk_key;
 			u8 type;
 			u32 item_offset;
+			u32 item_size;
 
 			if (disk_item_offset + sizeof(struct btrfs_item) >
 			    sf->block_ctx->len) {
@@ -1047,6 +1048,7 @@ leaf_item_out_of_bounce_error:
 						     disk_item_offset,
 						     sizeof(struct btrfs_item));
 			item_offset = le32_to_cpu(disk_item.offset);
+			item_size = le32_to_cpu(disk_item.size);
 			disk_key = &disk_item.key;
 			type = disk_key->type;
 
@@ -1057,14 +1059,13 @@ leaf_item_out_of_bounce_error:
 
 				root_item_offset = item_offset +
 					offsetof(struct btrfs_leaf, items);
-				if (root_item_offset +
-				    sizeof(struct btrfs_root_item) >
+				if (root_item_offset + item_size >
 				    sf->block_ctx->len)
 					goto leaf_item_out_of_bounce_error;
 				btrfsic_read_from_block_data(
 					sf->block_ctx, &root_item,
 					root_item_offset,
-					sizeof(struct btrfs_root_item));
+					item_size);
 				next_bytenr = le64_to_cpu(root_item.bytenr);
 
 				sf->error =