Re: [PATCH v2 3/3] block: Improve blk_mq_get_sq_hctx()

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

On Wed, Jun 15, 2022 at 02:01:36PM -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
> blk_mq_get_sq_hctx() selects a hardware queue of type HCTX_TYPE_DEFAULT
> instead of a hardware queue of type HCTX_TYPE_READ.
> 
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> 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..7a5558bbc7f6 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 = ctx->hctxs[HCTX_TYPE_DEFAULT];
>  
>  	if (!blk_mq_hctx_stopped(hctx))
>  		return hctx;

Looks fine, since the original behavior is to return hctx with HCTX_TYPE_DEFAULT
before commit 5d05426e2d5f ("blk-mq: don't touch ->tagset in blk_mq_get_sq_hctx").

Reviewed-by: Ming Lei <ming.lei@redhat.com>



thanks,
Ming