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Commit c5248f79 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: remove support for stacking dm-mq on .request_fn device(s) 



Remove all fiddley code that propped up this support for a blk-mq
request-queue ontop of all .request_fn devices.

Testing has proven this niche request-based dm-mq mode to be buggy, when
testing fault tolerance with DM multipath, and there is no point trying
to preserve it.

Should help improve efficiency of pure dm-mq code and make code
maintenance less delicate.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 818c5f3b

drivers/md/dm-mpath.c

+4 −1
Original line number Diff line number Diff line
@@ -418,7 +418,10 @@ static int __multipath_map(struct dm_target *ti, struct request *clone, 
	spin_unlock_irq(&m->lock);



	if (clone) {

		/* Old request-based interface: allocated clone is passed in */

		/*

		 * Old request-based interface: allocated clone is passed in.

		 * Used by: .request_fn stacked on .request_fn path(s).

		 */

		clone->q = bdev_get_queue(bdev);

		clone->rq_disk = bdev->bd_disk;

		clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;

drivers/md/dm.c

+16 −39
Original line number Diff line number Diff line
@@ -1141,11 +1141,6 @@ static void free_rq_clone(struct request *clone) 
	else if (!md->queue->mq_ops)

		/* request_fn queue stacked on request_fn queue(s) */

		free_clone_request(md, clone);

	/*

	 * NOTE: for the blk-mq queue stacked on request_fn queue(s) case:

	 * no need to call free_clone_request() because we leverage blk-mq by

	 * allocating the clone at the end of the blk-mq pdu (see: clone_rq)

	 */



	if (!md->queue->mq_ops)

		free_rq_tio(tio);
@@ -1866,23 +1861,17 @@ static struct request *clone_rq(struct request *rq, struct mapped_device *md, 
				struct dm_rq_target_io *tio, gfp_t gfp_mask)

{

	/*

	 * Do not allocate a clone if tio->clone was already set

	 * (see: dm_mq_queue_rq).

	 * Create clone for use with .request_fn request_queue

	 */

	bool alloc_clone = !tio->clone;

	struct request *clone;



	if (alloc_clone) {

	clone = alloc_clone_request(md, gfp_mask);

	if (!clone)

		return NULL;

	} else

		clone = tio->clone;



	blk_rq_init(NULL, clone);

	if (setup_clone(clone, rq, tio, gfp_mask)) {

		/* -ENOMEM */

		if (alloc_clone)

		free_clone_request(md, clone);

		return NULL;

	}
@@ -2692,15 +2681,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, 
	 */

	tio->ti = ti;



	/*

	 * Both the table and md type cannot change after initial table load

	 */

	if (dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) {

		/* clone request is allocated at the end of the pdu */

		tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);

		(void) clone_rq(rq, md, tio, GFP_ATOMIC);

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

	} else {

	/* Direct call is fine since .queue_rq allows allocations */

	if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) {

		/* Undo dm_start_request() before requeuing */
@@ -2708,7 +2688,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, 
		rq_completed(md, rq_data_dir(rq), false);

		return BLK_MQ_RQ_QUEUE_BUSY;

	}

	}



	return BLK_MQ_RQ_QUEUE_OK;

}
@@ -2726,6 +2705,11 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md) 
	struct request_queue *q;

	int err;



	if (dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) {

		DMERR("request-based dm-mq may only be stacked on blk-mq device(s)");

		return -EINVAL;

	}



	md->tag_set = kzalloc(sizeof(struct blk_mq_tag_set), GFP_KERNEL);

	if (!md->tag_set)

		return -ENOMEM;
@@ -2738,10 +2722,6 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md) 
	md->tag_set->driver_data = md;



	md->tag_set->cmd_size = sizeof(struct dm_rq_target_io);

	if (md_type == DM_TYPE_REQUEST_BASED) {

		/* put the memory for non-blk-mq clone at the end of the pdu */

		md->tag_set->cmd_size += sizeof(struct request);

	}



	err = blk_mq_alloc_tag_set(md->tag_set);

	if (err)
@@ -2758,9 +2738,6 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md) 
	/* backfill 'mq' sysfs registration normally done in blk_register_queue */

	blk_mq_register_disk(md->disk);



	if (md_type == DM_TYPE_REQUEST_BASED)

		init_rq_based_worker_thread(md);



	return 0;



out_tag_set: