Commit 2eb6e1e3 authored by Keith Busch's avatar Keith Busch Committed by Mike Snitzer
Browse files

dm: submit stacked requests in irq enabled context 



Switch to having request-based DM enqueue all prep'ed requests into work
processed by another thread.  This allows request-based DM to invoke
block APIs that assume interrupt enabled context (e.g. blk_get_request)
and is a prerequisite for adding blk-mq support to request-based DM.

The new kernel thread is only initialized for request-based DM devices.

multipath_map() is now always in irq enabled context so change multipath
spinlock (m->lock) locking to always disable interrupts.

Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 1ae49ea2

drivers/md/dm-mpath.c

+11 −7
Original line number Diff line number Diff line
@@ -384,12 +384,11 @@ static int multipath_map(struct dm_target *ti, struct request *clone, 
	struct multipath *m = (struct multipath *) ti->private;

	int r = DM_MAPIO_REQUEUE;

	size_t nr_bytes = blk_rq_bytes(clone);

	unsigned long flags;

	struct pgpath *pgpath;

	struct block_device *bdev;

	struct dm_mpath_io *mpio;



	spin_lock_irqsave(&m->lock, flags);

	spin_lock_irq(&m->lock);



	/* Do we need to select a new pgpath? */

	if (!m->current_pgpath ||
@@ -411,21 +410,26 @@ static int multipath_map(struct dm_target *ti, struct request *clone, 
		/* ENOMEM, requeue */

		goto out_unlock;



	mpio = map_context->ptr;

	mpio->pgpath = pgpath;

	mpio->nr_bytes = nr_bytes;



	bdev = pgpath->path.dev->bdev;



	clone->q = bdev_get_queue(bdev);

	clone->rq_disk = bdev->bd_disk;

	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;

	mpio = map_context->ptr;

	mpio->pgpath = pgpath;

	mpio->nr_bytes = nr_bytes;



	spin_unlock_irq(&m->lock);



	if (pgpath->pg->ps.type->start_io)

		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,

					      &pgpath->path,

					      nr_bytes);

	r = DM_MAPIO_REMAPPED;

	return DM_MAPIO_REMAPPED;



out_unlock:

	spin_unlock_irqrestore(&m->lock, flags);

	spin_unlock_irq(&m->lock);



	return r;

}

drivers/md/dm.c

+35 −11
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/hdreg.h>

#include <linux/delay.h>

#include <linux/wait.h>

#include <linux/kthread.h>



#include <trace/events/block.h>
@@ -79,6 +80,7 @@ struct dm_rq_target_io { 
	struct mapped_device *md;

	struct dm_target *ti;

	struct request *orig, *clone;

	struct kthread_work work;

	int error;

	union map_info info;

};
@@ -208,6 +210,9 @@ struct mapped_device { 
	struct bio flush_bio;



	struct dm_stats stats;



	struct kthread_worker kworker;

	struct task_struct *kworker_task;

};



/*
@@ -1773,6 +1778,8 @@ static struct request *__clone_rq(struct request *rq, struct mapped_device *md, 
	return clone;

}



static void map_tio_request(struct kthread_work *work);



static struct request *clone_rq(struct request *rq, struct mapped_device *md,

				gfp_t gfp_mask)

{
@@ -1789,6 +1796,7 @@ static struct request *clone_rq(struct request *rq, struct mapped_device *md, 
	tio->orig = rq;

	tio->error = 0;

	memset(&tio->info, 0, sizeof(tio->info));

	init_kthread_work(&tio->work, map_tio_request);



	clone = __clone_rq(rq, md, tio, GFP_ATOMIC);

	if (!clone) {
@@ -1833,7 +1841,6 @@ static int map_request(struct dm_target *ti, struct request *clone, 
	int r, requeued = 0;

	struct dm_rq_target_io *tio = clone->end_io_data;



	tio->ti = ti;

	r = ti->type->map_rq(ti, clone, &tio->info);

	switch (r) {

	case DM_MAPIO_SUBMITTED:
@@ -1864,6 +1871,13 @@ static int map_request(struct dm_target *ti, struct request *clone, 
	return requeued;

}



static void map_tio_request(struct kthread_work *work)

{

	struct dm_rq_target_io *tio = container_of(work, struct dm_rq_target_io, work);



	map_request(tio->ti, tio->clone, tio->md);

}



static struct request *dm_start_request(struct mapped_device *md, struct request *orig)

{

	struct request *clone;
@@ -1895,6 +1909,7 @@ static void dm_request_fn(struct request_queue *q) 
	struct dm_table *map = dm_get_live_table(md, &srcu_idx);

	struct dm_target *ti;

	struct request *rq, *clone;

	struct dm_rq_target_io *tio;

	sector_t pos;



	/*
@@ -1930,20 +1945,15 @@ static void dm_request_fn(struct request_queue *q) 


		clone = dm_start_request(md, rq);



		spin_unlock(q->queue_lock);

		if (map_request(ti, clone, md))

			goto requeued;



		tio = rq->special;

		/* Establish tio->ti before queuing work (map_tio_request) */

		tio->ti = ti;

		queue_kthread_work(&md->kworker, &tio->work);

		BUG_ON(!irqs_disabled());

		spin_lock(q->queue_lock);

	}



	goto out;



requeued:

	BUG_ON(!irqs_disabled());

	spin_lock(q->queue_lock);



delay_and_out:

	blk_delay_queue(q, HZ / 10);

out:
@@ -2129,6 +2139,7 @@ static struct mapped_device *alloc_dev(int minor) 
	INIT_WORK(&md->work, dm_wq_work);

	init_waitqueue_head(&md->eventq);

	init_completion(&md->kobj_holder.completion);

	md->kworker_task = NULL;



	md->disk->major = _major;

	md->disk->first_minor = minor;
@@ -2189,6 +2200,9 @@ static void free_dev(struct mapped_device *md) 
	unlock_fs(md);

	bdput(md->bdev);

	destroy_workqueue(md->wq);



	if (md->kworker_task)

		kthread_stop(md->kworker_task);

	if (md->io_pool)

		mempool_destroy(md->io_pool);

	if (md->rq_pool)
@@ -2484,6 +2498,11 @@ static int dm_init_request_based_queue(struct mapped_device *md) 
	blk_queue_prep_rq(md->queue, dm_prep_fn);

	blk_queue_lld_busy(md->queue, dm_lld_busy);



	/* Also initialize the request-based DM worker thread */

	init_kthread_worker(&md->kworker);

	md->kworker_task = kthread_run(kthread_worker_fn, &md->kworker,

				       "kdmwork-%s", dm_device_name(md));



	elv_register_queue(md->queue);



	return 1;
@@ -2574,6 +2593,9 @@ static void __dm_destroy(struct mapped_device *md, bool wait) 
	set_bit(DMF_FREEING, &md->flags);

	spin_unlock(&_minor_lock);



	if (dm_request_based(md))

		flush_kthread_worker(&md->kworker);



	if (!dm_suspended_md(md)) {

		dm_table_presuspend_targets(map);

		dm_table_postsuspend_targets(map);
@@ -2817,8 +2839,10 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map, 
	 * Stop md->queue before flushing md->wq in case request-based

	 * dm defers requests to md->wq from md->queue.

	 */

	if (dm_request_based(md))

	if (dm_request_based(md)) {

		stop_queue(md->queue);

		flush_kthread_worker(&md->kworker);

	}



	flush_workqueue(md->wq);

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