In order to gracefully handle split-brain scenario which are very
unlikely, yet possible, while performing the FSID change I'm
gonna need two more pieces of information:
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@xxxxxxxx>
---
fs/btrfs/volumes.c | 9 ++++++++-
fs/btrfs/volumes.h | 5 +++++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index bf0aa900f22c..f9dcbe74093c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -785,6 +785,8 @@ 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);
@@ -798,6 +800,8 @@ 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);
@@ -904,8 +908,11 @@ 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(found_transid,
+ fs_devices->latest_generation);
+ }
fs_devices->total_devices = btrfs_super_num_devices(disk_super);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 04860497b33c..6b2a01c55426 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
--
2.7.4
