Re: [PATCH RFC 5/6] md/raid1: Handle bio_split() errors

[John Garry <john.g.garry@oracle.com>]

On 24/10/2024 03:10, Yu Kuai wrote:
>> On 23/10/2024 12:46, Geoff Back wrote:
>>>>> Yes, raid1/raid10 write are the same. If you want to enable atomic 
>>>>> write
>>>>> for raid1/raid10, you must add a new branch to handle badblocks now,
>>>>> otherwise, as long as one copy contain any badblocks, atomic write 
>>>>> will
>>>>> fail while theoretically I think it can work.
>>>> Can you please expand on what you mean by this last sentence, "I think
>>>> it can work".
> 
> I mean in this case, for the write IO, there is no need to split this IO
> for the underlying disks that doesn't have BB, hence atomic write can
> still work. Currently solution is to split the IO to the range that all
> underlying disks doesn't have BB.

ok, right.

> 
>>>>
>>>> Indeed, IMO, chance of encountering a device with BBs and supporting
>>>> atomic writes is low, so no need to try to make it work (if it were
>>>> possible) - I think that we just report EIO.
> 
> If you want this, then make sure raid will set fail fast together with
> atomic write. This way disk will just faulty with IO error instead of
> marking with BB, hence make sure there are no BBs.

To be clear, you mean to set the r1/r10 bio failfast flag, right? There 
are rdev and also r1/r10 bio failfast flags.

Thanks,
John