Re: [PATCH 5/6] btrfs: copy fsid and metadata_uuid for pulled disk without INCOMPAT_METADATA_UUID

[Su Yue <Damenly_Su@gmx.com>]

On 2020/1/6 11:12 PM, Nikolay Borisov wrote:
>
>
> On 12.12.19 г. 13:01 ч., damenly.su@gmail.com wrote:
>> From: Su Yue <Damenly_Su@gmx.com>
>>
>> Since a scanned device may be the device pulled into disk without
>> metadata_uuid feature, there may already be changing devices there.
>> Here copy fsid and metadata_uuid for above case.
>>
>> Signed-off-by: Su Yue <Damenly_Su@gmx.com>
>
>
> What does this patch fix, why is it needed? It seems to be independent
> of the split brain fixes?
>

Sorry for the messy and short commit log.
It's one of the split brain fixes.

As mails I replied you earlier, the case
is for device which succeed to sync in
the second transaction and is without
metadata_uuid feature. If there is fs_devices
already scanned, the device's fsid instead of
metadata_uuid(NULL here) should be copied into
the fs_devices->metada_uuid field.

Thanks.

>> ---
>>   fs/btrfs/volumes.c | 11 +++++++----
>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index faf9cdd14f33..b21ab45e76a0 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -964,13 +964,16 @@ static noinline struct btrfs_device *device_list_add(const char *path,
>>   	 * metadata_uuid/fsid values of the fs_devices.
>>   	 */
>>   	if (*new_device_added && fs_devices_found &&
>> -	    has_metadata_uuid && fs_devices->fsid_change &&
>> +	    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);
>> -
>> +		if (has_metadata_uuid)
>> +			memcpy(fs_devices->metadata_uuid,
>> +			       disk_super->metadata_uuid, BTRFS_FSID_SIZE);
>> +		else
>> +			memcpy(fs_devices->metadata_uuid,
>> +			       disk_super->fsid, BTRFS_FSID_SIZE);
>>   		fs_devices->fsid_change = false;
>>   	}
>>
>>