blk-mq: do limited block plug for multiple queue case (f984df1f) · Commits · 戴 / test

block/blk-mq.c

+59 −23

Original line number	Diff line number	Diff line
		@@ -1224,6 +1224,38 @@ static struct request blk_mq_map_request(struct request_queue q,
		return rq;
		}

		static int blk_mq_direct_issue_request(struct request *rq)
		{
		int ret;
		struct request_queue *q = rq->q;
		struct blk_mq_hw_ctx *hctx = q->mq_ops->map_queue(q,
		rq->mq_ctx->cpu);
		struct blk_mq_queue_data bd = {
		.rq = rq,
		.list = NULL,
		.last = 1
		};

		/*
		* For OK queue, we are done. For error, kill it. Any other
		* error (busy), just add it to our list as we previously
		* would have done
		*/
		ret = q->mq_ops->queue_rq(hctx, &bd);
		if (ret == BLK_MQ_RQ_QUEUE_OK)
		return 0;
		else {
		__blk_mq_requeue_request(rq);

		if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
		rq->errors = -EIO;
		blk_mq_end_request(rq, rq->errors);
		return 0;
		}
		return -1;
		}
		}

		/*
		* Multiple hardware queue variant. This will not use per-process plugs,
		* but will attempt to bypass the hctx queueing if we can go straight to
		@@ -1235,6 +1267,8 @@ static void blk_mq_make_request(struct request_queue q, struct bio bio)
		const int is_flush_fua = bio->bi_rw & (REQ_FLUSH \| REQ_FUA);
		struct blk_map_ctx data;
		struct request *rq;
		unsigned int request_count = 0;
		struct blk_plug *plug;

		blk_queue_bounce(q, &bio);

		@@ -1243,6 +1277,10 @@ static void blk_mq_make_request(struct request_queue q, struct bio bio)
		return;
		}

		if (!is_flush_fua && !blk_queue_nomerges(q) &&
		blk_attempt_plug_merge(q, bio, &request_count))
		return;

		rq = blk_mq_map_request(q, bio, &data);
		if (unlikely(!rq))
		return;
		@@ -1253,40 +1291,39 @@ static void blk_mq_make_request(struct request_queue q, struct bio bio)
		goto run_queue;
		}

		plug = current->plug;
		/*
		* If the driver supports defer issued based on 'last', then
		* queue it up like normal since we can potentially save some
		* CPU this way.
		*/
		if (is_sync && !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) {
		struct blk_mq_queue_data bd = {
		.rq = rq,
		.list = NULL,
		.last = 1
		};
		int ret;
		if (((plug && !blk_queue_nomerges(q)) \|\| is_sync) &&
		!(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) {
		struct request *old_rq = NULL;

		blk_mq_bio_to_request(rq, bio);

		/*
		* For OK queue, we are done. For error, kill it. Any other
		* error (busy), just add it to our list as we previously
		* would have done
		* we do limited pluging. If bio can be merged, do merge.
		* Otherwise the existing request in the plug list will be
		* issued. So the plug list will have one request at most
		*/
		ret = q->mq_ops->queue_rq(data.hctx, &bd);
		if (ret == BLK_MQ_RQ_QUEUE_OK)
		goto done;
		else {
		__blk_mq_requeue_request(rq);

		if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
		rq->errors = -EIO;
		blk_mq_end_request(rq, rq->errors);
		goto done;
		if (plug) {
		if (!list_empty(&plug->mq_list)) {
		old_rq = list_first_entry(&plug->mq_list,
		struct request, queuelist);
		list_del_init(&old_rq->queuelist);
		}
		blk_mq_insert_request(rq, false, true, true);
		list_add_tail(&rq->queuelist, &plug->mq_list);
		} else /* is_sync */
		old_rq = rq;
		blk_mq_put_ctx(data.ctx);
		if (!old_rq)
		return;
		if (!blk_mq_direct_issue_request(old_rq))
		return;
		blk_mq_insert_request(old_rq, false, true, true);
		return;
		}
		}

		if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
		@@ -1299,7 +1336,6 @@ static void blk_mq_make_request(struct request_queue q, struct bio bio)
		run_queue:
		blk_mq_run_hw_queue(data.hctx, !is_sync \|\| is_flush_fua);
		}
		done:
		blk_mq_put_ctx(data.ctx);
		}

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