Re: [PATCH V3 3/4] md/raid10: improve raid10 discard request

[Xiao Ni <xni@redhat.com>]

On 08/21/2020 06:13 AM, Song Liu wrote:
> On Thu, Aug 20, 2020 at 12:22 AM Xiao Ni <xni@redhat.com> wrote:
> [...]
>
>> +
>> +       if (conf->reshape_progress != MaxSector &&
>> +           ((bio->bi_iter.bi_sector >= conf->reshape_progress) !=
>> +            conf->mddev->reshape_backwards))
>> +               geo = conf->prev;
>> +
>> +       stripe_size = (1<<geo.chunk_shift) * geo.raid_disks;
>>
>> This could be raid_disks << chunk_shift
>>
>> +       stripe_mask = stripe_size - 1;
>>
>> Does this work when raid_disks is not power of 2?
>>
>> In test I used 5 disks to create the raid10 too, it worked well. Could you explain what
>> you worried in detail?
> Say we have geo.raid_disks == 5, and geo.chunk_shift == 8. Then we get
> stripe_size == 0x500 and stripe_mask == 0x4ff == b'100 1111 1111
> Is this the proper stripe_mask?
>
> Thanks,
> Song
>
I got it. Thanks very much. It can't use mask here to justify whether 
start/end address is aligned
with stripe size. It should check whether it's a multiple of stripe 
size. I'll send patch again after
fixing all problems.

Regards
Xiao