Re: [PATCH 3/3] block: Specify the operation type when calling blk_mq_map_queue()

[Ming Lei <ming.lei@redhat.com>]

On Tue, Jun 14, 2022 at 10:57:25AM -0700, Bart Van Assche wrote:
> Since the introduction of blk_mq_get_hctx_type() the operation type in
> the second argument of blk_mq_get_hctx_type() matters. Make sure that
> a hardware queue of type HCTX_TYPE_DEFAULT is selected instead of a
> hardware queue of type HCTX_TYPE_READ.
> 
> Cc: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/blk-mq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e9bf950983c7..9b1518ef1aa1 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2168,7 +2168,7 @@ static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
>  	 * just causes lock contention inside the scheduler and pointless cache
>  	 * bouncing.
>  	 */
> -	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, 0, ctx);
> +	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, REQ_OP_WRITE, ctx);

The change itself doesn't make a difference, since both results in choosing
HCTX_TYPE_DEFAULT, but passing REQ_OP_WRITE is a bit misleading.


Thanks,
Ming