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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>
This commit is contained in:
Nikolay Borisov 2018-10-30 16:43:26 +02:00 committed by David Sterba
parent fbc6feaec9
commit d1a6300282
2 changed files with 13 additions and 1 deletions
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9
fs/btrfs/volumes.c
View File

@ -792,6 +792,8 @@ static noinline struct btrfs_device *device_list_add(const char *path,
u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) &
BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
if (has_metadata_uuid)
fs_devices = find_fsid(disk_super->fsid, disk_super->metadata_uuid);
@ -805,6 +807,8 @@ static noinline struct btrfs_device *device_list_add(const char *path,
else
fs_devices = alloc_fs_devices(disk_super->fsid, NULL);
fs_devices->fsid_change = fsid_change_in_progress;
if (IS_ERR(fs_devices))
return ERR_CAST(fs_devices);
@ -940,8 +944,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
* it back. We need it to pick the disk with largest generation
* (as above).
*/
if (!fs_devices->opened)
if (!fs_devices->opened) {
device->generation = found_transid;
fs_devices->latest_generation = max_t(u64, found_transid,
fs_devices->latest_generation);
}
fs_devices->total_devices = btrfs_super_num_devices(disk_super);

5
fs/btrfs/volumes.h
View File

@ -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