btrfs: add members to fs_devices to track fsid changes
In order to gracefully handle split-brain scenario during fsid change
(which are very unlikely, yet possible), two more pieces of information
will be necessary:
1. The highest generation number among all devices registered to a
particular btrfs_fs_devices
2. A boolean flag whether a given btrfs_fs_devices was created by a
device which had the FSID_CHANGING_V2 flag set.
This is a preparatory patch and just introduces the variables as well
as code which sets them, their actual use is going to happen in a later
patch.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index bdee4b6..1d936ce 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -211,6 +211,7 @@ BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
struct btrfs_fs_devices {
u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
u8 metadata_uuid[BTRFS_FSID_SIZE];
+ bool fsid_change;
struct list_head fs_list;
u64 num_devices;
@@ -219,6 +220,10 @@ struct btrfs_fs_devices {
u64 missing_devices;
u64 total_rw_bytes;
u64 total_devices;
+
+ /* Highest generation number of seen devices */
+ u64 latest_generation;
+
struct block_device *latest_bdev;
/* all of the devices in the FS, protected by a mutex