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From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
	Ming Lei <ming.lei@redhat.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Keith Busch <keith.busch@intel.com>
Subject: [PATCH V2 RESEND 4/5] blk-mq: re-submit IO in case that hctx is dead
Date: Sun,  6 Oct 2019 10:45:15 +0800	[thread overview]
Message-ID: <20191006024516.19996-5-ming.lei@redhat.com> (raw)
In-Reply-To: <20191006024516.19996-1-ming.lei@redhat.com>

When all CPUs in one hctx are offline, we shouldn't run this hw queue
for completing request any more.

So steal bios from the request, and resubmit them, and finally free
the request in blk_mq_hctx_notify_dead().

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d991c122abf2..0b35fdbd1f17 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
 	return 0;
 }
 
+static void blk_mq_resubmit_io(struct request *rq)
+{
+	struct bio_list list;
+	struct bio *bio;
+
+	bio_list_init(&list);
+	blk_steal_bios(&list, rq);
+
+	while (true) {
+		bio = bio_list_pop(&list);
+		if (!bio)
+			break;
+
+		generic_make_request(bio);
+	}
+
+	blk_mq_cleanup_rq(rq);
+	blk_mq_end_request(rq, 0);
+}
+
 /*
- * 'cpu' is going away. splice any existing rq_list entries from this
- * software queue to the hw queue dispatch list, and ensure that it
- * gets run.
+ * 'cpu' has gone away. If this hctx is dead, we can't dispatch request
+ * to the hctx any more, so steal bios from requests of this hctx, and
+ * re-submit them to the request queue, and free these requests finally.
  */
 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 {
@@ -2291,6 +2311,8 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 	struct blk_mq_ctx *ctx;
 	LIST_HEAD(tmp);
 	enum hctx_type type;
+	bool hctx_dead;
+	struct request *rq;
 
 	hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
 	ctx = __blk_mq_get_ctx(hctx->queue, cpu);
@@ -2298,6 +2320,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 
 	clear_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state);
 
+	hctx_dead = cpumask_first_and(hctx->cpumask, cpu_online_mask) >=
+		nr_cpu_ids;
+
 	spin_lock(&ctx->lock);
 	if (!list_empty(&ctx->rq_lists[type])) {
 		list_splice_init(&ctx->rq_lists[type], &tmp);
@@ -2308,11 +2333,20 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 	if (list_empty(&tmp))
 		return 0;
 
-	spin_lock(&hctx->lock);
-	list_splice_tail_init(&tmp, &hctx->dispatch);
-	spin_unlock(&hctx->lock);
+	if (!hctx_dead) {
+		spin_lock(&hctx->lock);
+		list_splice_tail_init(&tmp, &hctx->dispatch);
+		spin_unlock(&hctx->lock);
+		blk_mq_run_hw_queue(hctx, true);
+		return 0;
+	}
+
+	while (!list_empty(&tmp)) {
+		rq = list_entry(tmp.next, struct request, queuelist);
+		list_del_init(&rq->queuelist);
+		blk_mq_resubmit_io(rq);
+	}
 
-	blk_mq_run_hw_queue(hctx, true);
 	return 0;
 }
 
-- 
2.20.1


  parent reply	other threads:[~2019-10-06  2:45 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-06  2:45 [PATCH V2 RESEND 0/5] blk-mq: improvement on handling IO during CPU hotplug Ming Lei
2019-10-06  2:45 ` [PATCH V2 RESEND 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei
2019-10-07  6:02   ` Hannes Reinecke
2019-10-06  2:45 ` [PATCH V2 RESEND 2/5] blk-mq: add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ Ming Lei
2019-10-07  6:06   ` Hannes Reinecke
2019-10-06  2:45 ` [PATCH V2 RESEND 3/5] blk-mq: stop to handle IO before hctx's all CPUs become offline Ming Lei
2019-10-07  6:23   ` Hannes Reinecke
2019-10-07 15:01     ` Ming Lei
2019-10-07 10:23   ` John Garry
2019-10-07 15:04     ` Ming Lei
2019-10-07 16:49       ` John Garry
2019-10-06  2:45 ` Ming Lei [this message]
2019-10-07  6:27   ` [PATCH V2 RESEND 4/5] blk-mq: re-submit IO in case that hctx is dead Hannes Reinecke
2019-10-07 15:05     ` Ming Lei
2019-10-06  2:45 ` [PATCH V2 RESEND 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei
2019-10-07  6:28   ` Hannes Reinecke

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