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Commit 2527d997 authored by Jens Axboe's avatar Jens Axboe
Browse files

elevator: lookup mq vs non-mq elevators 

If an IO scheduler is selected via elevator= and it doesn't match
the driver in question wrt blk-mq support, then we fail to boot.

The elevator= parameter is deprecated and only supported for
non-mq devices. Augment the elevator lookup API so that we
pass in if we're looking for an mq capable scheduler or not,
so that we only ever return a valid type for the queue in
question.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196695


Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d5ce4c31

block/elevator.c

+21 −23
Original line number Diff line number Diff line
@@ -83,12 +83,15 @@ bool elv_bio_merge_ok(struct request *rq, struct bio *bio) 
}

EXPORT_SYMBOL(elv_bio_merge_ok);



static struct elevator_type *elevator_find(const char *name)

/*

 * Return scheduler with name 'name' and with matching 'mq capability

 */

static struct elevator_type *elevator_find(const char *name, bool mq)

{

	struct elevator_type *e;



	list_for_each_entry(e, &elv_list, list) {

		if (!strcmp(e->elevator_name, name))

		if (!strcmp(e->elevator_name, name) && (mq == e->uses_mq))

			return e;

	}
@@ -100,25 +103,25 @@ static void elevator_put(struct elevator_type *e) 
	module_put(e->elevator_owner);

}



static struct elevator_type *elevator_get(const char *name, bool try_loading)

static struct elevator_type *elevator_get(struct request_queue *q,

					  const char *name, bool try_loading)

{

	struct elevator_type *e;



	spin_lock(&elv_list_lock);



	e = elevator_find(name);

	e = elevator_find(name, q->mq_ops != NULL);

	if (!e && try_loading) {

		spin_unlock(&elv_list_lock);

		request_module("%s-iosched", name);

		spin_lock(&elv_list_lock);

		e = elevator_find(name);

		e = elevator_find(name, q->mq_ops != NULL);

	}



	if (e && !try_module_get(e->elevator_owner))

		e = NULL;



	spin_unlock(&elv_list_lock);



	return e;

}
@@ -144,8 +147,12 @@ void __init load_default_elevator_module(void) 
	if (!chosen_elevator[0])

		return;



	/*

	 * Boot parameter is deprecated, we haven't supported that for MQ.

	 * Only look for non-mq schedulers from here.

	 */

	spin_lock(&elv_list_lock);

	e = elevator_find(chosen_elevator);

	e = elevator_find(chosen_elevator, false);

	spin_unlock(&elv_list_lock);



	if (!e)
@@ -202,7 +209,7 @@ int elevator_init(struct request_queue *q, char *name) 
	q->boundary_rq = NULL;



	if (name) {

		e = elevator_get(name, true);

		e = elevator_get(q, name, true);

		if (!e)

			return -EINVAL;

	}
@@ -214,7 +221,7 @@ int elevator_init(struct request_queue *q, char *name) 
	 * allowed from async.

	 */

	if (!e && !q->mq_ops && *chosen_elevator) {

		e = elevator_get(chosen_elevator, false);

		e = elevator_get(q, chosen_elevator, false);

		if (!e)

			printk(KERN_ERR "I/O scheduler %s not found\n",

							chosen_elevator);
@@ -229,17 +236,17 @@ int elevator_init(struct request_queue *q, char *name) 
		 */

		if (q->mq_ops) {

			if (q->nr_hw_queues == 1)

				e = elevator_get("mq-deadline", false);

				e = elevator_get(q, "mq-deadline", false);

			if (!e)

				return 0;

		} else

			e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);

			e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);



		if (!e) {

			printk(KERN_ERR

				"Default I/O scheduler not found. " \

				"Using noop.\n");

			e = elevator_get("noop", false);

			e = elevator_get(q, "noop", false);

		}

	}
@@ -905,7 +912,7 @@ int elv_register(struct elevator_type *e) 


	/* register, don't allow duplicate names */

	spin_lock(&elv_list_lock);

	if (elevator_find(e->elevator_name)) {

	if (elevator_find(e->elevator_name, e->uses_mq)) {

		spin_unlock(&elv_list_lock);

		if (e->icq_cache)

			kmem_cache_destroy(e->icq_cache);
@@ -1066,7 +1073,7 @@ static int __elevator_change(struct request_queue *q, const char *name) 
		return elevator_switch(q, NULL);



	strlcpy(elevator_name, name, sizeof(elevator_name));

	e = elevator_get(strstrip(elevator_name), true);

	e = elevator_get(q, strstrip(elevator_name), true);

	if (!e)

		return -EINVAL;
@@ -1076,15 +1083,6 @@ static int __elevator_change(struct request_queue *q, const char *name) 
		return 0;

	}



	if (!e->uses_mq && q->mq_ops) {

		elevator_put(e);

		return -EINVAL;

	}

	if (e->uses_mq && !q->mq_ops) {

		elevator_put(e);

		return -EINVAL;

	}



	return elevator_switch(q, e);

}