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From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Jeffle Xu <jefflexu@linux.alibaba.com>,
	Ming Lei <ming.lei@redhat.com>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	"Wunderlich, Mark" <mark.wunderlich@intel.com>,
	"Vasudevan, Anil" <anil.vasudevan@intel.com>,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 05/15] blk-mq: factor out a "classic" poll helper
Date: Tue, 27 Apr 2021 18:16:09 +0200	[thread overview]
Message-ID: <20210427161619.1294399-6-hch@lst.de> (raw)
In-Reply-To: <20210427161619.1294399-1-hch@lst.de>

Factor the code to do the classic full metal polling out of blk_poll into
a separate blk_mq_poll_classic helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-mq.c | 120 +++++++++++++++++++++++--------------------------
 1 file changed, 56 insertions(+), 64 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 06a43fb5e2c5..ba563ca57bd9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -69,6 +69,14 @@ static inline struct blk_mq_hw_ctx *blk_qc_to_hctx(struct request_queue *q,
 	return q->queue_hw_ctx[(qc & ~BLK_QC_T_INTERNAL) >> BLK_QC_T_SHIFT];
 }
 
+static inline struct request *blk_qc_to_rq(struct blk_mq_hw_ctx *hctx,
+		blk_qc_t qc)
+{
+	if (blk_qc_t_is_internal(qc))
+		return blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(qc));
+	return blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(qc));
+}
+
 /*
  * Check if any of the ctx, dispatch list or elevator
  * have pending work in this hardware queue.
@@ -3781,15 +3789,20 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
 	return ret;
 }
 
-static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
-				     struct request *rq)
+static bool blk_mq_poll_hybrid(struct request_queue *q, blk_qc_t qc)
 {
+	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, qc);
+	struct request *rq = blk_qc_to_rq(hctx, qc);
 	struct hrtimer_sleeper hs;
 	enum hrtimer_mode mode;
 	unsigned int nsecs;
 	ktime_t kt;
 
-	if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
+	/*
+	 * If a request has completed on queue that uses an I/O scheduler, we
+	 * won't get back a request from blk_qc_to_rq.
+	 */
+	if (!rq || (rq->rq_flags & RQF_MQ_POLL_SLEPT))
 		return false;
 
 	/*
@@ -3831,32 +3844,48 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
 
 	__set_current_state(TASK_RUNNING);
 	destroy_hrtimer_on_stack(&hs.timer);
+
+	/*
+	 * If we sleep, have the caller restart the poll loop to reset the
+	 * state.  Like for the other success return cases, the caller is
+	 * responsible for checking if the IO completed.  If the IO isn't
+	 * complete, we'll get called again and will go straight to the busy
+	 * poll loop.
+	 */
 	return true;
 }
 
-static bool blk_mq_poll_hybrid(struct request_queue *q,
-			       struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
+static int blk_mq_poll_classic(struct request_queue *q, blk_qc_t cookie,
+		bool spin)
 {
-	struct request *rq;
+	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, cookie);
+	long state = current->state;
+	int ret;
 
-	if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
-		return false;
+	hctx->poll_considered++;
 
-	if (!blk_qc_t_is_internal(cookie))
-		rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
-	else {
-		rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
-		/*
-		 * With scheduling, if the request has completed, we'll
-		 * get a NULL return here, as we clear the sched tag when
-		 * that happens. The request still remains valid, like always,
-		 * so we should be safe with just the NULL check.
-		 */
-		if (!rq)
-			return false;
-	}
+	do {
+		hctx->poll_invoked++;
 
-	return blk_mq_poll_hybrid_sleep(q, rq);
+		ret = q->mq_ops->poll(hctx);
+		if (ret > 0) {
+			hctx->poll_success++;
+			__set_current_state(TASK_RUNNING);
+			return ret;
+		}
+
+		if (signal_pending_state(state, current))
+			__set_current_state(TASK_RUNNING);
+		if (current->state == TASK_RUNNING)
+			return 1;
+
+		if (ret < 0 || !spin)
+			break;
+		cpu_relax();
+	} while (!need_resched());
+
+	__set_current_state(TASK_RUNNING);
+	return 0;
 }
 
 /**
@@ -3873,9 +3902,6 @@ static bool blk_mq_poll_hybrid(struct request_queue *q,
  */
 int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 {
-	struct blk_mq_hw_ctx *hctx;
-	long state;
-
 	if (!blk_qc_t_valid(cookie) ||
 	    !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
 		return 0;
@@ -3883,46 +3909,12 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 	if (current->plug)
 		blk_flush_plug_list(current->plug, false);
 
-	hctx = blk_qc_to_hctx(q, cookie);
-
-	/*
-	 * If we sleep, have the caller restart the poll loop to reset
-	 * the state. Like for the other success return cases, the
-	 * caller is responsible for checking if the IO completed. If
-	 * the IO isn't complete, we'll get called again and will go
-	 * straight to the busy poll loop. If specified not to spin,
-	 * we also should not sleep.
-	 */
-	if (spin && blk_mq_poll_hybrid(q, hctx, cookie))
-		return 1;
-
-	hctx->poll_considered++;
-
-	state = current->state;
-	do {
-		int ret;
-
-		hctx->poll_invoked++;
-
-		ret = q->mq_ops->poll(hctx);
-		if (ret > 0) {
-			hctx->poll_success++;
-			__set_current_state(TASK_RUNNING);
-			return ret;
-		}
-
-		if (signal_pending_state(state, current))
-			__set_current_state(TASK_RUNNING);
-
-		if (current->state == TASK_RUNNING)
+	/* If specified not to spin, we also should not sleep. */
+	if (spin && q->poll_nsec != BLK_MQ_POLL_CLASSIC) {
+		if (blk_mq_poll_hybrid(q, cookie))
 			return 1;
-		if (ret < 0 || !spin)
-			break;
-		cpu_relax();
-	} while (!need_resched());
-
-	__set_current_state(TASK_RUNNING);
-	return 0;
+	}
+	return blk_mq_poll_classic(q, cookie, spin);
 }
 EXPORT_SYMBOL_GPL(blk_poll);
 
-- 
2.30.1


  parent reply	other threads:[~2021-04-27 16:20 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-27 16:16 switch block layer polling to a bio based model v2 Christoph Hellwig
2021-04-27 16:16 ` [PATCH 01/15] direct-io: remove blk_poll support Christoph Hellwig
2021-04-27 16:16 ` [PATCH 02/15] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO Christoph Hellwig
2021-04-27 16:16 ` [PATCH 03/15] iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw Christoph Hellwig
2021-04-27 16:16 ` [PATCH 04/15] blk-mq: factor out a blk_qc_to_hctx helper Christoph Hellwig
2021-04-27 16:16 ` Christoph Hellwig [this message]
2021-04-27 16:16 ` [PATCH 06/15] blk-mq: remove blk_qc_t_to_tag and blk_qc_t_is_internal Christoph Hellwig
2021-04-27 16:16 ` [PATCH 07/15] blk-mq: remove blk_qc_t_valid Christoph Hellwig
2021-04-27 16:16 ` [PATCH 08/15] io_uring: don't sleep when polling for I/O Christoph Hellwig
2021-04-27 16:16 ` [PATCH 09/15] block: rename REQ_HIPRI to REQ_POLLED Christoph Hellwig
2021-04-27 16:16 ` [PATCH 10/15] block: use SLAB_TYPESAFE_BY_RCU for the bio slab Christoph Hellwig
2021-04-27 16:16 ` [PATCH 11/15] block: define 'struct bvec_iter' as packed Christoph Hellwig
2021-04-27 16:16 ` [PATCH 12/15] block: switch polling to be bio based Christoph Hellwig
2021-04-28  2:28   ` Ming Lei
2021-04-29  7:20     ` Christoph Hellwig
2021-04-29  7:36       ` Ming Lei
2021-04-29  9:50         ` Christoph Hellwig
2021-04-29 14:42           ` Ming Lei
2021-04-27 16:16 ` [PATCH 13/15] block: add a QUEUE_FLAG_POLL_CAPABLE flag Christoph Hellwig
2021-04-27 16:16 ` [PATCH 14/15] nvme-multipath: set QUEUE_FLAG_NOWAIT Christoph Hellwig
2021-04-28  2:32   ` Ming Lei
2021-04-29  7:27     ` Christoph Hellwig
2021-04-29  7:37       ` Ming Lei
2021-04-29  9:46         ` Christoph Hellwig
2021-05-06 21:23           ` Sagi Grimberg
2021-04-27 16:16 ` [PATCH 15/15] nvme-multipath: enable polled I/O Christoph Hellwig
2021-04-28  2:36   ` Ming Lei
2021-05-12 13:15 switch block layer polling to a bio based model v3 Christoph Hellwig
2021-05-12 13:15 ` [PATCH 05/15] blk-mq: factor out a "classic" poll helper Christoph Hellwig
2021-05-12 20:59   ` Sagi Grimberg

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