linux-kernel - Re: [PATCH v5 5/6] dm-stripe: limit chunk

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Message-ID: <54dc7fac-0e79-4ed1-bb7b-54962441b2a1@oracle.com>
Date: Thu, 10 Jul 2025 16:29:00 +0100
From: John Garry <john.g.garry@...cle.com>
To: Mikulas Patocka <mpatocka@...hat.com>
Cc: agk@...hat.com, snitzer@...nel.org, song@...nel.org, yukuai3@...wei.com,
        hch@....de, nilay@...ux.ibm.com, axboe@...nel.dk, cem@...nel.org,
        dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-block@...r.kernel.org,
        ojaswin@...ux.ibm.com, martin.petersen@...cle.com,
        akpm@...ux-foundation.org, linux-xfs@...r.kernel.org,
        djwong@...nel.org
Subject: Re: [PATCH v5 5/6] dm-stripe: limit chunk_sectors to the stripe size

On 10/07/2025 16:03, Mikulas Patocka wrote:
> 
> 
> On Wed, 9 Jul 2025, John Garry wrote:
> 
>> Same as done for raid0, set chunk_sectors limit to appropriately set the
>> atomic write size limit.
>>
>> Setting chunk_sectors limit in this way overrides the stacked limit
>> already calculated based on the bottom device limits. This is ok, as
>> when any bios are sent to the bottom devices, the block layer will still
>> respect the bottom device chunk_sectors.
>>
>> Reviewed-by: Nilay Shroff <nilay@...ux.ibm.com>
>> Reviewed-by: Mikulas Patocka <mpatocka@...hat.com>
>> Signed-off-by: John Garry <john.g.garry@...cle.com>
>> ---
>>   drivers/md/dm-stripe.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
>> index a7dc04bd55e5..5bbbdf8fc1bd 100644
>> --- a/drivers/md/dm-stripe.c
>> +++ b/drivers/md/dm-stripe.c
>> @@ -458,6 +458,7 @@ static void stripe_io_hints(struct dm_target *ti,
>>   	struct stripe_c *sc = ti->private;
>>   	unsigned int chunk_size = sc->chunk_size << SECTOR_SHIFT;
>>   
>> +	limits->chunk_sectors = sc->chunk_size;
>>   	limits->io_min = chunk_size;
>>   	limits->io_opt = chunk_size * sc->stripes;
>>   }
>> -- 
>> 2.43.5
> 
> Hi
> 
> This will conflict with the current dm code in linux-dm.git. Should I fix
> up the conflict and commit it through the linux-dm git?

I was hoping that Jens would take this series through the block tree, so 
I will let him comment.

But I think that taking this patch separately though linux-dm would 
create an intermediate breakage for atomics functionality for dm-stripe 
on the block tree. Not many are using it yet, so not an utterly terrible 
a way to go.

Thanks,
John