On Wed, 3 Mar 2021, JeffleXu wrote:
>
>
> On 3/3/21 3:05 AM, Mikulas Patocka wrote:
> > Don't clear REQ_HIPRI for bio-based drivers. Device mapper will need to
> > see this flag in order to support polling.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> >
> > ---
> > block/blk-core.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-2.6/block/blk-core.c
> > ===================================================================
> > --- linux-2.6.orig/block/blk-core.c 2021-03-02 10:43:28.000000000 +0100
> > +++ linux-2.6/block/blk-core.c 2021-03-02 10:53:50.000000000 +0100
>
> I notice that the diff header indicates that the code base is from
> linux-2.6. Or it's just the name of your directory, while the code base
> is for the latest upstream 5.12?
It's just the name of the git repository. The patch is against 5.12-rc1.
>
> > @@ -836,7 +836,7 @@ static noinline_for_stack bool submit_bi
> > }
> > }
> >
> > - if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
> > + if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && !bdev->bd_disk->fops->submit_bio)
> > bio->bi_opf &= ~REQ_HIPRI;
> >
> > switch (bio_op(bio)) {
> >
> > --
>
> What if dm device is built upon mq devices that are not capable of
> polling, i.e., mq devices without QUEUE_FLAG_POLL set? Then this dm
> device shall not support polling.
We will check if the underlying queue has QUEUE_FLAG_POLL in __map_bio -
see this piece of code:
case DM_MAPIO_REMAPPED:
/* the bio has been remapped so dispatch it */
trace_block_bio_remap(clone, bio_dev(io->orig_bio), sector);
if (clone->bi_opf & REQ_HIPRI &&
test_bit(QUEUE_FLAG_POLL, &clone->bi_bdev->bd_disk->queue->queue_flags)) {
ci->poll_queue = clone->bi_bdev->bd_disk->queue;
ci->poll_cookie = submit_bio_noacct_mq_direct(clone);
} else {
ci->poll_cookie = BLK_QC_T_NONE;
submit_bio_noacct(clone);
}
break;
Mikulas
