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Commit a6a252e6 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-mq-sched: decide how to handle flush rq via RQF_FLUSH_SEQ 



In case of IO scheduler we always pre-allocate one driver tag before
calling blk_insert_flush(), and flush request will be marked as
RQF_FLUSH_SEQ once it is in flush machinery.

So if RQF_FLUSH_SEQ isn't set, we call blk_insert_flush() to handle
the request, otherwise the flush request is dispatched to ->dispatch
list directly.

This is a preparation patch for not preallocating a driver tag for flush
requests, and for not treating flush requests as a special case. This is
similar to what the legacy path does.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 598906f8

block/blk-mq-sched.c

+16 −13
Original line number Diff line number Diff line
@@ -345,23 +345,25 @@ void blk_mq_sched_request_inserted(struct request *rq) 
EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);



static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,

				       bool has_sched,

				       struct request *rq)

{

	if (rq->tag == -1) {

		rq->rq_flags |= RQF_SORTED;

		return false;

	}



	/*

	 * If we already have a real request tag, send directly to

	 * the dispatch list.

	 */

	/* dispatch flush rq directly */

	if (rq->rq_flags & RQF_FLUSH_SEQ) {

		spin_lock(&hctx->lock);

		list_add(&rq->queuelist, &hctx->dispatch);

		spin_unlock(&hctx->lock);

		return true;

	}



	if (has_sched) {

		rq->rq_flags |= RQF_SORTED;

		WARN_ON(rq->tag != -1);

	}



	return false;

}



/*

 * Add flush/fua to the queue. If we fail getting a driver tag, then

 * punt to the requeue list. Requeue will re-invoke us from a context
@@ -385,12 +387,13 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head, 
	struct blk_mq_ctx *ctx = rq->mq_ctx;

	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);



	if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {

	/* flush rq in flush machinery need to be dispatched directly */

	if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {

		blk_mq_sched_insert_flush(hctx, rq, can_block);

		return;

	}



	if (e && blk_mq_sched_bypass_insert(hctx, rq))

	if (blk_mq_sched_bypass_insert(hctx, !!e, rq))

		goto run;



	if (e && e->type->ops.mq.insert_requests) {
@@ -428,7 +431,7 @@ void blk_mq_sched_insert_requests(struct request_queue *q, 
		list_for_each_entry_safe(rq, next, list, queuelist) {

			if (WARN_ON_ONCE(rq->tag != -1)) {

				list_del_init(&rq->queuelist);

				blk_mq_sched_bypass_insert(hctx, rq);

				blk_mq_sched_bypass_insert(hctx, true, rq);

			}

		}

	}