Re: [PATCH 1/2] md/raid0,raid4,raid5,raid6,raid10: fix bogus io_opt value

[Tony Battersby <tonyb@cybernetics.com>]

On 7/29/25 12:56, Yu Kuai wrote:
> Hi,
>
> 在 2025/7/30 0:12, Tony Battersby 写道:
>> md-raid currently sets io_min and io_opt to the RAID chunk and stripe
>> sizes and then calls queue_limits_stack_bdev() to combine the io_min and
>> io_opt values with those of the component devices.  The io_opt size is
>> notably combined using the least common multiple (lcm), which does not
>> work well in practice for some drives (1), resulting in overflow or
>> unreasonable values.
>>
>> dm-raid, on the other hand, sets io_min and io_opt through the
>> raid_io_hints() function, which is called after stacking all the queue
>> limits of the component drives, so the RAID chunk and stripe sizes
>> override the values of the stacking.
>>
>> Change md-raid to be more like dm-raid by setting io_min and io_opt to
>> the RAID chunk and stripe sizes after stacking the queue limits of the
>> component devies.  This fixes /sys/block/md0/queue/optimal_io_size from
>> being a bogus value like 3221127168 to being the correct RAID stripe
>> size.
> This is already discussed, and mtp3sas should fix this strange value.

Thanks, I will follow that ongoing discussion.

https://lore.kernel.org/all/ywsfp3lqnijgig6yrlv2ztxram6ohf5z4yfeebswjkvp2dzisd@f5ikoyo3sfq5/