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

[Su Yue <Damenly_Su@gmx.com>]

On 2020/1/7 3:18 PM, Nikolay Borisov wrote:
>
>
> On 7.01.20 г. 3:31 ч., Su Yue wrote:
>> 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.
>
> I figures as much as I started tackling the problem. So this must be
> part of the patch which fixes aforementioned split brain scenario. I
> have already developed some patches + tests. So will be sending those,
> since they are very similar to what you posted originally I will retain
> your SOB line.
>

I'm okay about this way. Thanks.
>>
>> 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;
>>>>        }
>>>>
>>>>
>>