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Commit e3bde04f authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Mike Snitzer
Browse files

dm mpath: reduce memory pressure when requeuing 



When multipath needs to requeue I/O in the block layer the per-request
context shouldn't be allocated, as it will be freed immediately
afterwards anyway.  Avoiding this memory allocation will reduce memory
pressure during requeuing.

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 3e9f1be1

drivers/md/dm-mpath.c

+15 −23
Original line number Diff line number Diff line
@@ -378,12 +378,12 @@ static int __must_push_back(struct multipath *m) 
static int map_io(struct multipath *m, struct request *clone,

		  union map_info *map_context)

{

	int r = DM_MAPIO_REMAPPED;

	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 = map_context->ptr;

	struct dm_mpath_io *mpio;



	spin_lock_irqsave(&m->lock, flags);
@@ -396,27 +396,29 @@ static int map_io(struct multipath *m, struct request *clone, 


	if (pgpath) {

		if (pg_ready(m)) {

			if (set_mapinfo(m, map_context) < 0)

				/* ENOMEM, requeue */

				goto out_unlock;



			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;

			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;

			r = DM_MAPIO_REMAPPED;

			goto out_unlock;

		}

	} else {

		/* No path */

		if (__must_push_back(m))

			r = DM_MAPIO_REQUEUE;

		else

		__pg_init_all_paths(m);

	} else if (!__must_push_back(m))

		r = -EIO;	/* Failed */

	}



out_unlock:

	spin_unlock_irqrestore(&m->lock, flags);



	return r;
@@ -912,19 +914,9 @@ static void multipath_dtr(struct dm_target *ti) 
static int multipath_map(struct dm_target *ti, struct request *clone,

			 union map_info *map_context)

{

	int r;

	struct multipath *m = (struct multipath *) ti->private;



	if (set_mapinfo(m, map_context) < 0)

		/* ENOMEM, requeue */

		return DM_MAPIO_REQUEUE;



	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;

	r = map_io(m, clone, map_context);

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

		clear_mapinfo(m, map_context);



	return r;

	return map_io(m, clone, map_context);

}



/*