[PATCH V2 05/13] block: only account passthrough IO from userspace

[Ming Lei]

On Wed, Jan 26, 2022 at 09:49:50AM +0100, Christoph Hellwig wrote:
> On Wed, Jan 26, 2022 at 04:33:54PM +0800, Ming Lei wrote:
> > > I guess you are worried about the latter conditionin that we stop
> > > accounting for no data transfer passthrough commands?
> > 
> > No, I meant that bio->bi_bdev isn't setup yet for passthrough request,
> > and not sure that can be done easily.
> 
> Take a look at e.g. nvme_submit_user_cmd and iblock_get_bio.

nvme just sets part0 to rq->bio, which is fine since nvme doesn't
support partial completion.

The simplest way could be to assign bio->bi_bdev with q->disk->part0 in both
bio_copy_user_iov() and bio_map_user_iov(), which should cover most of cases.
Given user io is always on device instead of partition even though the
command is sent via partition bdev.


Thanks,
Ming