Re: [PATCH] block: check bio alignment in blk_mq_submit_bio

[Hannes Reinecke <hare@suse.de>]

On 6/19/24 05:34, Ming Lei wrote:
> IO logical block size is one fundamental queue limit, and every IO has
> to be aligned with logical block size because our bio split can't deal
> with unaligned bio.
> 
> The check has to be done with queue usage counter grabbed because device
> reconfiguration may change logical block size, and we can prevent the
> reconfiguration from happening by holding queue usage counter.
> 
> logical_block_size stays in the 1st cache line of queue_limits, and this
> cache line is always fetched in fast path via bio_may_exceed_limits(),
> so IO perf won't be affected by this check.
> 
> Cc: Yi Zhang <yi.zhang@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Ye Bin <yebin10@huawei.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
Is this still an issue after the atomic queue limits patchset from 
Christoph?
One of the changes there is that we now always freeze the queue before
changing any limits.
So really this check should never trigger.

Hmm?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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