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Commit d48ece20 authored by Jianchao Wang's avatar Jianchao Wang Committed by Jens Axboe
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blk-mq: init hctx sched after update ctx and hctx mapping 



Currently, when update nr_hw_queues, IO scheduler's init_hctx will
be invoked before the mapping between ctx and hctx is adapted
correctly by blk_mq_map_swqueue. The IO scheduler init_hctx (kyber)
may depend on this mapping and get wrong result and panic finally.
A simply way to fix this is that switch the IO scheduler to 'none'
before update the nr_hw_queues, and then switch it back after
update nr_hw_queues. blk_mq_sched_init_/exit_hctx are removed due
to nobody use them any more.

Signed-off-by: default avatarJianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fcedba42

block/blk-mq-sched.c

+0 −44
Original line number Diff line number Diff line
@@ -462,50 +462,6 @@ static void blk_mq_sched_tags_teardown(struct request_queue *q) 
		blk_mq_sched_free_tags(set, hctx, i);

}



int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,

			   unsigned int hctx_idx)

{

	struct elevator_queue *e = q->elevator;

	int ret;



	if (!e)

		return 0;



	ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);

	if (ret)

		return ret;



	if (e->type->ops.mq.init_hctx) {

		ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);

		if (ret) {

			blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);

			return ret;

		}

	}



	blk_mq_debugfs_register_sched_hctx(q, hctx);



	return 0;

}



void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,

			    unsigned int hctx_idx)

{

	struct elevator_queue *e = q->elevator;



	if (!e)

		return;



	blk_mq_debugfs_unregister_sched_hctx(hctx);



	if (e->type->ops.mq.exit_hctx && hctx->sched_data) {

		e->type->ops.mq.exit_hctx(hctx, hctx_idx);

		hctx->sched_data = NULL;

	}



	blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);

}



int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)

{

	struct blk_mq_hw_ctx *hctx;

block/blk-mq-sched.h

+0 −5
Original line number Diff line number Diff line
@@ -28,11 +28,6 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx); 
int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e);

void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);



int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,

			   unsigned int hctx_idx);

void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,

			    unsigned int hctx_idx);



static inline bool

blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)

{

block/blk-mq.c

+84 −8
Original line number Diff line number Diff line
@@ -2147,8 +2147,6 @@ static void blk_mq_exit_hctx(struct request_queue *q, 
	if (set->ops->exit_request)

		set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);



	blk_mq_sched_exit_hctx(q, hctx, hctx_idx);



	if (set->ops->exit_hctx)

		set->ops->exit_hctx(hctx, hctx_idx);
@@ -2216,12 +2214,9 @@ static int blk_mq_init_hctx(struct request_queue *q, 
	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))

		goto free_bitmap;



	if (blk_mq_sched_init_hctx(q, hctx, hctx_idx))

		goto exit_hctx;



	hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);

	if (!hctx->fq)

		goto sched_exit_hctx;

		goto exit_hctx;



	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))

		goto free_fq;
@@ -2235,8 +2230,6 @@ static int blk_mq_init_hctx(struct request_queue *q, 


 free_fq:

	kfree(hctx->fq);

 sched_exit_hctx:

	blk_mq_sched_exit_hctx(q, hctx, hctx_idx);

 exit_hctx:

	if (set->ops->exit_hctx)

		set->ops->exit_hctx(hctx, hctx_idx);
@@ -2898,10 +2891,81 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) 
	return ret;

}



/*

 * request_queue and elevator_type pair.

 * It is just used by __blk_mq_update_nr_hw_queues to cache

 * the elevator_type associated with a request_queue.

 */

struct blk_mq_qe_pair {

	struct list_head node;

	struct request_queue *q;

	struct elevator_type *type;

};



/*

 * Cache the elevator_type in qe pair list and switch the

 * io scheduler to 'none'

 */

static bool blk_mq_elv_switch_none(struct list_head *head,

		struct request_queue *q)

{

	struct blk_mq_qe_pair *qe;



	if (!q->elevator)

		return true;



	qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);

	if (!qe)

		return false;



	INIT_LIST_HEAD(&qe->node);

	qe->q = q;

	qe->type = q->elevator->type;

	list_add(&qe->node, head);



	mutex_lock(&q->sysfs_lock);

	/*

	 * After elevator_switch_mq, the previous elevator_queue will be

	 * released by elevator_release. The reference of the io scheduler

	 * module get by elevator_get will also be put. So we need to get

	 * a reference of the io scheduler module here to prevent it to be

	 * removed.

	 */

	__module_get(qe->type->elevator_owner);

	elevator_switch_mq(q, NULL);

	mutex_unlock(&q->sysfs_lock);



	return true;

}



static void blk_mq_elv_switch_back(struct list_head *head,

		struct request_queue *q)

{

	struct blk_mq_qe_pair *qe;

	struct elevator_type *t = NULL;



	list_for_each_entry(qe, head, node)

		if (qe->q == q) {

			t = qe->type;

			break;

		}



	if (!t)

		return;



	list_del(&qe->node);

	kfree(qe);



	mutex_lock(&q->sysfs_lock);

	elevator_switch_mq(q, t);

	mutex_unlock(&q->sysfs_lock);

}



static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,

							int nr_hw_queues)

{

	struct request_queue *q;

	LIST_HEAD(head);



	lockdep_assert_held(&set->tag_list_lock);
@@ -2912,6 +2976,14 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 


	list_for_each_entry(q, &set->tag_list, tag_set_list)

		blk_mq_freeze_queue(q);

	/*

	 * Switch IO scheduler to 'none', cleaning up the data associated

	 * with the previous scheduler. We will switch back once we are done

	 * updating the new sw to hw queue mappings.

	 */

	list_for_each_entry(q, &set->tag_list, tag_set_list)

		if (!blk_mq_elv_switch_none(&head, q))

			goto switch_back;



	set->nr_hw_queues = nr_hw_queues;

	blk_mq_update_queue_map(set);
@@ -2920,6 +2992,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 
		blk_mq_queue_reinit(q);

	}



switch_back:

	list_for_each_entry(q, &set->tag_list, tag_set_list)

		blk_mq_elv_switch_back(&head, q);



	list_for_each_entry(q, &set->tag_list, tag_set_list)

		blk_mq_unfreeze_queue(q);

}

block/blk.h

+2 −0
Original line number Diff line number Diff line
@@ -234,6 +234,8 @@ static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq 


int elevator_init(struct request_queue *);

int elevator_init_mq(struct request_queue *q);

int elevator_switch_mq(struct request_queue *q,

			      struct elevator_type *new_e);

void elevator_exit(struct request_queue *, struct elevator_queue *);

int elv_register_queue(struct request_queue *q);

void elv_unregister_queue(struct request_queue *q);

block/elevator.c

+12 −8
Original line number Diff line number Diff line
@@ -933,16 +933,13 @@ void elv_unregister(struct elevator_type *e) 
}

EXPORT_SYMBOL_GPL(elv_unregister);



static int elevator_switch_mq(struct request_queue *q,

int elevator_switch_mq(struct request_queue *q,

			      struct elevator_type *new_e)

{

	int ret;



	lockdep_assert_held(&q->sysfs_lock);



	blk_mq_freeze_queue(q);

	blk_mq_quiesce_queue(q);



	if (q->elevator) {

		if (q->elevator->registered)

			elv_unregister_queue(q);
@@ -968,8 +965,6 @@ static int elevator_switch_mq(struct request_queue *q, 
		blk_add_trace_msg(q, "elv switch: none");



out:

	blk_mq_unquiesce_queue(q);

	blk_mq_unfreeze_queue(q);

	return ret;

}
@@ -1021,8 +1016,17 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 


	lockdep_assert_held(&q->sysfs_lock);



	if (q->mq_ops)

		return elevator_switch_mq(q, new_e);

	if (q->mq_ops) {

		blk_mq_freeze_queue(q);

		blk_mq_quiesce_queue(q);



		err = elevator_switch_mq(q, new_e);



		blk_mq_unquiesce_queue(q);

		blk_mq_unfreeze_queue(q);



		return err;

	}



	/*

	 * Turn on BYPASS and drain all requests w/ elevator private data.