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Commit 6fca6a61 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-mq: add helper to insert requests from irq context 



Both the cache flush state machine and the SCSI midlayer want to submit
requests from irq context, and the current per-request requeue_work
unfortunately causes corruption due to sharing with the csd field for
flushes.  Replace them with a per-request_queue list of requests to
be requeued.

Based on an earlier test by Ming Lei.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reported-by: default avatarMing Lei <tom.leiming@gmail.com>
Tested-by: default avatarMing Lei <tom.leiming@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 7738dac4

block/blk-flush.c

+4 −12
Original line number Diff line number Diff line
@@ -130,21 +130,13 @@ static void blk_flush_restore_request(struct request *rq) 
	blk_clear_rq_complete(rq);

}



static void mq_flush_run(struct work_struct *work)

{

	struct request *rq;



	rq = container_of(work, struct request, requeue_work);



	memset(&rq->csd, 0, sizeof(rq->csd));

	blk_mq_insert_request(rq, false, true, false);

}



static bool blk_flush_queue_rq(struct request *rq, bool add_front)

{

	if (rq->q->mq_ops) {

		INIT_WORK(&rq->requeue_work, mq_flush_run);

		kblockd_schedule_work(&rq->requeue_work);

		struct request_queue *q = rq->q;



		blk_mq_add_to_requeue_list(rq, add_front);

		blk_mq_kick_requeue_list(q);

		return false;

	} else {

		if (add_front)

block/blk-mq.c

+63 −1
Original line number Diff line number Diff line
@@ -516,10 +516,68 @@ void blk_mq_requeue_request(struct request *rq) 
	blk_clear_rq_complete(rq);



	BUG_ON(blk_queued_rq(rq));

	blk_mq_insert_request(rq, true, true, false);

	blk_mq_add_to_requeue_list(rq, true);

}

EXPORT_SYMBOL(blk_mq_requeue_request);



static void blk_mq_requeue_work(struct work_struct *work)

{

	struct request_queue *q =

		container_of(work, struct request_queue, requeue_work);

	LIST_HEAD(rq_list);

	struct request *rq, *next;

	unsigned long flags;



	spin_lock_irqsave(&q->requeue_lock, flags);

	list_splice_init(&q->requeue_list, &rq_list);

	spin_unlock_irqrestore(&q->requeue_lock, flags);



	list_for_each_entry_safe(rq, next, &rq_list, queuelist) {

		if (!(rq->cmd_flags & REQ_SOFTBARRIER))

			continue;



		rq->cmd_flags &= ~REQ_SOFTBARRIER;

		list_del_init(&rq->queuelist);

		blk_mq_insert_request(rq, true, false, false);

	}



	while (!list_empty(&rq_list)) {

		rq = list_entry(rq_list.next, struct request, queuelist);

		list_del_init(&rq->queuelist);

		blk_mq_insert_request(rq, false, false, false);

	}



	blk_mq_run_queues(q, false);

}



void blk_mq_add_to_requeue_list(struct request *rq, bool at_head)

{

	struct request_queue *q = rq->q;

	unsigned long flags;



	/*

	 * We abuse this flag that is otherwise used by the I/O scheduler to

	 * request head insertation from the workqueue.

	 */

	BUG_ON(rq->cmd_flags & REQ_SOFTBARRIER);



	spin_lock_irqsave(&q->requeue_lock, flags);

	if (at_head) {

		rq->cmd_flags |= REQ_SOFTBARRIER;

		list_add(&rq->queuelist, &q->requeue_list);

	} else {

		list_add_tail(&rq->queuelist, &q->requeue_list);

	}

	spin_unlock_irqrestore(&q->requeue_lock, flags);

}

EXPORT_SYMBOL(blk_mq_add_to_requeue_list);



void blk_mq_kick_requeue_list(struct request_queue *q)

{

	kblockd_schedule_work(&q->requeue_work);

}

EXPORT_SYMBOL(blk_mq_kick_requeue_list);



struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)

{

	return tags->rqs[tag];
@@ -1812,6 +1870,10 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set) 


	q->sg_reserved_size = INT_MAX;



	INIT_WORK(&q->requeue_work, blk_mq_requeue_work);

	INIT_LIST_HEAD(&q->requeue_list);

	spin_lock_init(&q->requeue_lock);



	if (q->nr_hw_queues > 1)

		blk_queue_make_request(q, blk_mq_make_request);

	else

include/linux/blk-mq.h

+2 −0
Original line number Diff line number Diff line
@@ -172,6 +172,8 @@ void blk_mq_end_io(struct request *rq, int error); 
void __blk_mq_end_io(struct request *rq, int error);



void blk_mq_requeue_request(struct request *rq);

void blk_mq_add_to_requeue_list(struct request *rq, bool at_head);

void blk_mq_kick_requeue_list(struct request_queue *q);

void blk_mq_complete_request(struct request *rq);



void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);

include/linux/blkdev.h

+4 −1
Original line number Diff line number Diff line
@@ -99,7 +99,6 @@ struct request { 
	struct list_head queuelist;

	union {

		struct call_single_data csd;

		struct work_struct requeue_work;

		unsigned long fifo_time;

	};
@@ -463,6 +462,10 @@ struct request_queue { 
	struct request		*flush_rq;

	spinlock_t		mq_flush_lock;



	struct list_head	requeue_list;

	spinlock_t		requeue_lock;

	struct work_struct	requeue_work;



	struct mutex		sysfs_lock;



	int			bypass_depth;