On 12.12.19 г. 13:01 ч., damenly.su@xxxxxxxxx wrote:
<snip>
> Acutally, there are two devices in the fs. Device 2 with
> FSID_CHANGING_V2 allocated a fs_devices. But, device 1 found the
> fs_devices but failed to be added into since fs_devices->opened (
It's not clear why device 1 wasn't able to be added to the fs_devices
allocated by dev 2. Please elaborate?
> the thread is doing mount device 1). But device 1's fsid was copied
> to fs_devices->fsid then the assertion failed.
dev 1 fsid should be copied iff its transid is newer.
>
> The solution is that only if a new device was added into a existing
> fs_device, then the fs_devices->fsid is allowed to be rewritten.
fs_devices->fsid must be re-written by any device which is _newer_ w.r.t
to the transid.
>
> Fixes: 7a62d0f07377 ("btrfs: Handle one more split-brain scenario during fsid change")
> Signed-off-by: Su Yue <Damenly_Su@xxxxxxx>
> ---
> fs/btrfs/volumes.c | 36 +++++++++++++++++++++---------------
> 1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index d8e5560db285..9efa4123c335 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -732,6 +732,9 @@ static noinline struct btrfs_device *device_list_add(const char *path,
> BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
> bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
> BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
> + bool fs_devices_found = false;
> +
> + *new_device_added = false;
>
> if (fsid_change_in_progress) {
> if (!has_metadata_uuid) {
> @@ -772,24 +775,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
>
> device = NULL;
> } else {
> + fs_devices_found = true;
> +
> mutex_lock(&fs_devices->device_list_mutex);
> device = btrfs_find_device(fs_devices, devid,
> disk_super->dev_item.uuid, NULL, false);
> -
> - /*
> - * If this disk has been pulled into an fs devices created by
> - * a device which had the CHANGING_FSID_V2 flag then replace the
> - * metadata_uuid/fsid values of the fs_devices.
> - */
> - if (has_metadata_uuid && fs_devices->fsid_change &&
> - found_transid > fs_devices->latest_generation) {
> - memcpy(fs_devices->fsid, disk_super->fsid,
> - BTRFS_FSID_SIZE);
> - memcpy(fs_devices->metadata_uuid,
> - disk_super->metadata_uuid, BTRFS_FSID_SIZE);
> -
> - fs_devices->fsid_change = false;
> - }
> }
>
> if (!device) {
> @@ -912,6 +902,22 @@ static noinline struct btrfs_device *device_list_add(const char *path,
> }
> }
>
> + /*
> + * If the new added disk has been pulled into an fs devices created by
> + * a device which had the CHANGING_FSID_V2 flag then replace the
> + * metadata_uuid/fsid values of the fs_devices.
> + */
> + if (*new_device_added && fs_devices_found &&
> + has_metadata_uuid && fs_devices->fsid_change &&
> + found_transid > fs_devices->latest_generation) {
> + memcpy(fs_devices->fsid, disk_super->fsid,
> + BTRFS_FSID_SIZE);
> + memcpy(fs_devices->metadata_uuid,
> + disk_super->metadata_uuid, BTRFS_FSID_SIZE);
> +
> + fs_devices->fsid_change = false;
> + }
> +
> /*
> * Unmount does not free the btrfs_device struct but would zero
> * generation along with most of the other members. So just update
>
