[PATCH 1/4] block: add mq_ops->queue_rqs hook

[Christoph Hellwig]

This whole series seems to miss a linux-block cc..

On Wed, Dec 15, 2021 at 09:24:18AM -0700, Jens Axboe wrote:
> If we have a list of requests in our plug list, send it to the driver in
> one go, if possible. The driver must set mq_ops->queue_rqs() to support
> this, if not the usual one-by-one path is used.
> 
> Signed-off-by: Jens Axboe <axboe at kernel.dk>
> ---
>  block/blk-mq.c         | 26 +++++++++++++++++++++++---
>  include/linux/blk-mq.h |  8 ++++++++
>  2 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e02e7017db03..f24394cb2004 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2512,6 +2512,7 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
>  {
>  	struct blk_mq_hw_ctx *this_hctx;
>  	struct blk_mq_ctx *this_ctx;
> +	struct request *rq;
>  	unsigned int depth;
>  	LIST_HEAD(list);
>  
> @@ -2520,7 +2521,28 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
>  	plug->rq_count = 0;
>  
>  	if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
> +		struct request_queue *q;
> +
> +		rq = rq_list_peek(&plug->mq_list);
> +		q = rq->q;

Nit: I'd just drop the q local variable as it is rather pointless.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch at lst.de>