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Commit e8099177 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Mike Snitzer
Browse files

dm mpath: push back requests instead of queueing 



There is no reason why multipath needs to queue requests internally for
queue_if_no_path or pg_init; we should rather push them back onto the
request queue.

And while we're at it we can simplify the conditional statement in
map_io() to make it easier to read.

Since mpath no longer does internal queuing of I/O the table info no
longer emits the internal queue_size.  Instead it displays 1 if queuing
is being used or 0 if it is not.

Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Reviewed-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
parent 9974fa2c

drivers/md/dm-mpath.c

+36 −78
Original line number Diff line number Diff line
@@ -93,9 +93,7 @@ struct multipath { 
	unsigned pg_init_count;		/* Number of times pg_init called */

	unsigned pg_init_delay_msecs;	/* Number of msecs before pg_init retry */



	unsigned queue_size;

	struct work_struct process_queued_ios;

	struct list_head queued_ios;



	struct work_struct trigger_event;
@@ -124,6 +122,7 @@ static struct workqueue_struct *kmultipathd, *kmpath_handlerd; 
static void process_queued_ios(struct work_struct *work);

static void trigger_event(struct work_struct *work);

static void activate_path(struct work_struct *work);

static int __pgpath_busy(struct pgpath *pgpath);





/*-----------------------------------------------
@@ -195,7 +194,6 @@ static struct multipath *alloc_multipath(struct dm_target *ti) 
	m = kzalloc(sizeof(*m), GFP_KERNEL);

	if (m) {

		INIT_LIST_HEAD(&m->priority_groups);

		INIT_LIST_HEAD(&m->queued_ios);

		spin_lock_init(&m->lock);

		m->queue_io = 1;

		m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
@@ -368,12 +366,15 @@ static void __choose_pgpath(struct multipath *m, size_t nr_bytes) 
 */

static int __must_push_back(struct multipath *m)

{

	return (m->queue_if_no_path != m->saved_queue_if_no_path &&

		dm_noflush_suspending(m->ti));

	return (m->queue_if_no_path ||

		(m->queue_if_no_path != m->saved_queue_if_no_path &&

		 dm_noflush_suspending(m->ti)));

}



#define pg_ready(m) (!(m)->queue_io && !(m)->pg_init_required)



static int map_io(struct multipath *m, struct request *clone,

		  union map_info *map_context, unsigned was_queued)

		  union map_info *map_context)

{

	int r = DM_MAPIO_REMAPPED;

	size_t nr_bytes = blk_rq_bytes(clone);
@@ -391,37 +392,28 @@ static int map_io(struct multipath *m, struct request *clone, 


	pgpath = m->current_pgpath;



	if (was_queued)

		m->queue_size--;



	if (m->pg_init_required) {

		if (!m->pg_init_in_progress)

			queue_work(kmultipathd, &m->process_queued_ios);

		r = DM_MAPIO_REQUEUE;

	} else if ((pgpath && m->queue_io) ||

		   (!pgpath && m->queue_if_no_path)) {

		/* Queue for the daemon to resubmit */

		list_add_tail(&clone->queuelist, &m->queued_ios);

		m->queue_size++;

		if (!m->queue_io)

			queue_work(kmultipathd, &m->process_queued_ios);

		pgpath = NULL;

		r = DM_MAPIO_SUBMITTED;

	} else if (pgpath) {

	if (pgpath) {

		if (pg_ready(m)) {

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

			clone->q = bdev_get_queue(bdev);

			clone->rq_disk = bdev->bd_disk;

	} else if (__must_push_back(m))

		r = DM_MAPIO_REQUEUE;

	else

		r = -EIO;	/* Failed */



			mpio->pgpath = pgpath;

			mpio->nr_bytes = nr_bytes;



	if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)

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

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

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

							      &pgpath->path,

							      nr_bytes);

		} else {

			__pg_init_all_paths(m);

			r = DM_MAPIO_REQUEUE;

		}

	} else {

		/* No path */

		if (__must_push_back(m))

			r = DM_MAPIO_REQUEUE;

		else

			r = -EIO;	/* Failed */

	}



	spin_unlock_irqrestore(&m->lock, flags);
@@ -443,7 +435,7 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path, 
	else

		m->saved_queue_if_no_path = queue_if_no_path;

	m->queue_if_no_path = queue_if_no_path;

	if (!m->queue_if_no_path && m->queue_size)

	if (!m->queue_if_no_path)

		queue_work(kmultipathd, &m->process_queued_ios);



	spin_unlock_irqrestore(&m->lock, flags);
@@ -451,40 +443,6 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path, 
	return 0;

}



/*-----------------------------------------------------------------

 * The multipath daemon is responsible for resubmitting queued ios.

 *---------------------------------------------------------------*/



static void dispatch_queued_ios(struct multipath *m)

{

	int r;

	unsigned long flags;

	union map_info *info;

	struct request *clone, *n;

	LIST_HEAD(cl);



	spin_lock_irqsave(&m->lock, flags);

	list_splice_init(&m->queued_ios, &cl);

	spin_unlock_irqrestore(&m->lock, flags);



	list_for_each_entry_safe(clone, n, &cl, queuelist) {

		list_del_init(&clone->queuelist);



		info = dm_get_rq_mapinfo(clone);



		r = map_io(m, clone, info, 1);

		if (r < 0) {

			clear_mapinfo(m, info);

			dm_kill_unmapped_request(clone, r);

		} else if (r == DM_MAPIO_REMAPPED)

			dm_dispatch_request(clone);

		else if (r == DM_MAPIO_REQUEUE) {

			clear_mapinfo(m, info);

			dm_requeue_unmapped_request(clone);

		}

	}

}



static void process_queued_ios(struct work_struct *work)

{

	struct multipath *m =
@@ -509,7 +467,7 @@ static void process_queued_ios(struct work_struct *work) 


	spin_unlock_irqrestore(&m->lock, flags);

	if (!must_queue)

		dispatch_queued_ios(m);

		dm_table_run_md_queue_async(m->ti->table);

}



/*
@@ -987,7 +945,7 @@ static int multipath_map(struct dm_target *ti, struct request *clone, 
		return DM_MAPIO_REQUEUE;



	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;

	r = map_io(m, clone, map_context, 0);

	r = map_io(m, clone, map_context);

	if (r < 0 || r == DM_MAPIO_REQUEUE)

		clear_mapinfo(m, map_context);
@@ -1056,7 +1014,7 @@ static int reinstate_path(struct pgpath *pgpath) 


	pgpath->is_active = 1;



	if (!m->nr_valid_paths++ && m->queue_size) {

	if (!m->nr_valid_paths++) {

		m->current_pgpath = NULL;

		queue_work(kmultipathd, &m->process_queued_ios);

	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
@@ -1435,7 +1393,7 @@ static void multipath_status(struct dm_target *ti, status_type_t type, 


	/* Features */

	if (type == STATUSTYPE_INFO)

		DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);

		DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);

	else {

		DMEMIT("%u ", m->queue_if_no_path +

			      (m->pg_init_retries > 0) * 2 +
@@ -1686,7 +1644,7 @@ static int multipath_busy(struct dm_target *ti) 
	spin_lock_irqsave(&m->lock, flags);



	/* pg_init in progress, requeue until done */

	if (m->pg_init_in_progress) {

	if (!pg_ready(m)) {

		busy = 1;

		goto out;

	}
@@ -1739,7 +1697,7 @@ static int multipath_busy(struct dm_target *ti) 
 *---------------------------------------------------------------*/

static struct target_type multipath_target = {

	.name = "multipath",

	.version = {1, 6, 0},

	.version = {1, 7, 0},

	.module = THIS_MODULE,

	.ctr = multipath_ctr,

	.dtr = multipath_dtr,