Commit 82f402fe authored by Jens Axboe's avatar Jens Axboe
Browse files

null_blk: add support for shared tags 



Some storage drivers need to share tag sets between devices. It's
useful to be able to model that with null_blk, to find hangs or
performance issues.

Add a 'shared_tags' bool module parameter that. If that is set to
true and nr_devices is bigger than 1, all devices allocated will
share the same tag set.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent edf064e7

drivers/block/null_blk.c

+70 −42
Original line number Diff line number Diff line
@@ -35,7 +35,8 @@ struct nullb { 
	struct request_queue *q;

	struct gendisk *disk;

	struct nvm_dev *ndev;

	struct blk_mq_tag_set tag_set;

	struct blk_mq_tag_set *tag_set;

	struct blk_mq_tag_set __tag_set;

	struct hrtimer timer;

	unsigned int queue_depth;

	spinlock_t lock;
@@ -50,6 +51,7 @@ static struct mutex lock; 
static int null_major;

static int nullb_indexes;

static struct kmem_cache *ppa_cache;

static struct blk_mq_tag_set tag_set;



enum {

	NULL_IRQ_NONE		= 0,
@@ -109,7 +111,7 @@ static int bs = 512; 
module_param(bs, int, S_IRUGO);

MODULE_PARM_DESC(bs, "Block size (in bytes)");



static int nr_devices = 2;

static int nr_devices = 1;

module_param(nr_devices, int, S_IRUGO);

MODULE_PARM_DESC(nr_devices, "Number of devices to register");
@@ -121,6 +123,10 @@ static bool blocking; 
module_param(blocking, bool, S_IRUGO);

MODULE_PARM_DESC(blocking, "Register as a blocking blk-mq driver device");



static bool shared_tags;

module_param(shared_tags, bool, S_IRUGO);

MODULE_PARM_DESC(shared_tags, "Share tag set between devices for blk-mq");



static int irqmode = NULL_IRQ_SOFTIRQ;



static int null_set_irqmode(const char *str, const struct kernel_param *kp)
@@ -376,31 +382,8 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx, 
	return BLK_STS_OK;

}



static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)

{

	BUG_ON(!nullb);

	BUG_ON(!nq);



	init_waitqueue_head(&nq->wait);

	nq->queue_depth = nullb->queue_depth;

}



static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,

			  unsigned int index)

{

	struct nullb *nullb = data;

	struct nullb_queue *nq = &nullb->queues[index];



	hctx->driver_data = nq;

	null_init_queue(nullb, nq);

	nullb->nr_queues++;



	return 0;

}



static const struct blk_mq_ops null_mq_ops = {

	.queue_rq       = null_queue_rq,

	.init_hctx	= null_init_hctx,

	.complete	= null_softirq_done_fn,

};
@@ -592,8 +575,8 @@ static void null_del_dev(struct nullb *nullb) 
	else

		del_gendisk(nullb->disk);

	blk_cleanup_queue(nullb->q);

	if (queue_mode == NULL_Q_MQ)

		blk_mq_free_tag_set(&nullb->tag_set);

	if (queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)

		blk_mq_free_tag_set(nullb->tag_set);

	if (!use_lightnvm)

		put_disk(nullb->disk);

	cleanup_queues(nullb);
@@ -615,6 +598,32 @@ static const struct block_device_operations null_fops = { 
	.release =	null_release,

};



static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)

{

	BUG_ON(!nullb);

	BUG_ON(!nq);



	init_waitqueue_head(&nq->wait);

	nq->queue_depth = nullb->queue_depth;

}



static void null_init_queues(struct nullb *nullb)

{

	struct request_queue *q = nullb->q;

	struct blk_mq_hw_ctx *hctx;

	struct nullb_queue *nq;

	int i;



	queue_for_each_hw_ctx(q, hctx, i) {

		if (!hctx->nr_ctx || !hctx->tags)

			continue;

		nq = &nullb->queues[i];

		hctx->driver_data = nq;

		null_init_queue(nullb, nq);

		nullb->nr_queues++;

	}

}



static int setup_commands(struct nullb_queue *nq)

{

	struct nullb_cmd *cmd;
@@ -695,6 +704,22 @@ static int null_gendisk_register(struct nullb *nullb) 
	return 0;

}



static int null_init_tag_set(struct blk_mq_tag_set *set)

{

	set->ops = &null_mq_ops;

	set->nr_hw_queues = submit_queues;

	set->queue_depth = hw_queue_depth;

	set->numa_node = home_node;

	set->cmd_size	= sizeof(struct nullb_cmd);

	set->flags = BLK_MQ_F_SHOULD_MERGE;

	set->driver_data = NULL;



	if (blocking)

		set->flags |= BLK_MQ_F_BLOCKING;



	return blk_mq_alloc_tag_set(set);

}



static int null_add_dev(void)

{

	struct nullb *nullb;
@@ -716,26 +741,23 @@ static int null_add_dev(void) 
		goto out_free_nullb;



	if (queue_mode == NULL_Q_MQ) {

		nullb->tag_set.ops = &null_mq_ops;

		nullb->tag_set.nr_hw_queues = submit_queues;

		nullb->tag_set.queue_depth = hw_queue_depth;

		nullb->tag_set.numa_node = home_node;

		nullb->tag_set.cmd_size	= sizeof(struct nullb_cmd);

		nullb->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;

		nullb->tag_set.driver_data = nullb;



		if (blocking)

			nullb->tag_set.flags |= BLK_MQ_F_BLOCKING;

		if (shared_tags) {

			nullb->tag_set = &tag_set;

			rv = 0;

		} else {

			nullb->tag_set = &nullb->__tag_set;

			rv = null_init_tag_set(nullb->tag_set);

		}



		rv = blk_mq_alloc_tag_set(&nullb->tag_set);

		if (rv)

			goto out_cleanup_queues;



		nullb->q = blk_mq_init_queue(&nullb->tag_set);

		nullb->q = blk_mq_init_queue(nullb->tag_set);

		if (IS_ERR(nullb->q)) {

			rv = -ENOMEM;

			goto out_cleanup_tags;

		}

		null_init_queues(nullb);

	} else if (queue_mode == NULL_Q_BIO) {

		nullb->q = blk_alloc_queue_node(GFP_KERNEL, home_node);

		if (!nullb->q) {
@@ -788,8 +810,8 @@ static int null_add_dev(void) 
out_cleanup_blk_queue:

	blk_cleanup_queue(nullb->q);

out_cleanup_tags:

	if (queue_mode == NULL_Q_MQ)

		blk_mq_free_tag_set(&nullb->tag_set);

	if (queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)

		blk_mq_free_tag_set(nullb->tag_set);

out_cleanup_queues:

	cleanup_queues(nullb);

out_free_nullb:
@@ -822,6 +844,9 @@ static int __init null_init(void) 
		queue_mode = NULL_Q_MQ;

	}



	if (queue_mode == NULL_Q_MQ && shared_tags)

		null_init_tag_set(&tag_set);



	if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {

		if (submit_queues < nr_online_nodes) {

			pr_warn("null_blk: submit_queues param is set to %u.",
@@ -882,6 +907,9 @@ static void __exit null_exit(void) 
	}

	mutex_unlock(&lock);



	if (queue_mode == NULL_Q_MQ && shared_tags)

		blk_mq_free_tag_set(&tag_set);



	kmem_cache_destroy(ppa_cache);

}

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