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block: add mq_ops->queue_rqs hook

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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.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-12-03 06:48:53 -07:00
parent fcade2ce06
commit 3c67d44de7
2 changed files with 31 additions and 3 deletions
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26
block/blk-mq.c
View File

@ -2553,6 +2553,7 @@ 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);
@ -2561,7 +2562,28 @@ 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_list_peek(&plug->mq_list)->q;
struct request_queue *q;
rq = rq_list_peek(&plug->mq_list);
q = rq->q;
/*
* Peek first request and see if we have a ->queue_rqs() hook.
* If we do, we can dispatch the whole plug list in one go. We
* already know at this point that all requests belong to the
* same queue, caller must ensure that's the case.
*
* Since we pass off the full list to the driver at this point,
* we do not increment the active request count for the queue.
* Bypass shared tags for now because of that.
*/
if (q->mq_ops->queue_rqs &&
!(rq->mq_hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
blk_mq_run_dispatch_ops(q,
q->mq_ops->queue_rqs(&plug->mq_list));
if (rq_list_empty(plug->mq_list))
return;
}
blk_mq_run_dispatch_ops(q,
blk_mq_plug_issue_direct(plug, false));
@ -2573,8 +2595,6 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
this_ctx = NULL;
depth = 0;
do {
struct request *rq;
rq = rq_list_pop(&plug->mq_list);
if (!this_hctx) {

8
include/linux/blk-mq.h
View File

@ -492,6 +492,14 @@ struct blk_mq_ops {
*/
void (*commit_rqs)(struct blk_mq_hw_ctx *);
/**
* @queue_rqs: Queue a list of new requests. Driver is guaranteed
* that each request belongs to the same queue. If the driver doesn't
* empty the @rqlist completely, then the rest will be queued
* individually by the block layer upon return.
*/
void (*queue_rqs)(struct request **rqlist);
/**
* @get_budget: Reserve budget before queue request, once .queue_rq is
* run, it is driver's responsibility to release the