Re: [dm-devel] [PATCH 2/4] block: dont clear REQ_HIPRI for bio-based drivers

[JeffleXu <jefflexu@linux.alibaba.com>]

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@redhat.com>
> 
> ---
>  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?


> @@ -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.


-- 
Thanks,
Jeffle