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Commit f2298c04 authored by Jens Axboe's avatar Jens Axboe
Browse files

null_blk: multi queue aware block test driver 



A driver that simply completes IO it receives, it does no
transfers. Written to fascilitate testing of the blk-mq code.
It supports various module options to use either bio queueing,
rq queueing, or mq mode.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 320ae51f

drivers/block/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -15,6 +15,9 @@ menuconfig BLK_DEV 


if BLK_DEV



config BLK_DEV_NULL_BLK

	tristate "Null test block driver"



config BLK_DEV_FD

	tristate "Normal floppy disk support"

	depends on ARCH_MAY_HAVE_PC_FDC

drivers/block/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ obj-$(CONFIG_BLK_DEV_RBD) += rbd.o 
obj-$(CONFIG_BLK_DEV_PCIESSD_MTIP32XX)	+= mtip32xx/



obj-$(CONFIG_BLK_DEV_RSXX) += rsxx/

obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk.o



nvme-y		:= nvme-core.o nvme-scsi.o

swim_mod-y	:= swim.o swim_asm.o

drivers/block/null_blk.c

0 → 100644
+635 −0
Original line number Diff line number Diff line 
#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/sched.h>

#include <linux/fs.h>

#include <linux/blkdev.h>

#include <linux/init.h>

#include <linux/slab.h>

#include <linux/blk-mq.h>

#include <linux/hrtimer.h>



struct nullb_cmd {

	struct list_head list;

	struct llist_node ll_list;

	struct call_single_data csd;

	struct request *rq;

	struct bio *bio;

	unsigned int tag;

	struct nullb_queue *nq;

};



struct nullb_queue {

	unsigned long *tag_map;

	wait_queue_head_t wait;

	unsigned int queue_depth;



	struct nullb_cmd *cmds;

};



struct nullb {

	struct list_head list;

	unsigned int index;

	struct request_queue *q;

	struct gendisk *disk;

	struct hrtimer timer;

	unsigned int queue_depth;

	spinlock_t lock;



	struct nullb_queue *queues;

	unsigned int nr_queues;

};



static LIST_HEAD(nullb_list);

static struct mutex lock;

static int null_major;

static int nullb_indexes;



struct completion_queue {

	struct llist_head list;

	struct hrtimer timer;

};



/*

 * These are per-cpu for now, they will need to be configured by the

 * complete_queues parameter and appropriately mapped.

 */

static DEFINE_PER_CPU(struct completion_queue, completion_queues);



enum {

	NULL_IRQ_NONE		= 0,

	NULL_IRQ_SOFTIRQ	= 1,

	NULL_IRQ_TIMER		= 2,



	NULL_Q_BIO		= 0,

	NULL_Q_RQ		= 1,

	NULL_Q_MQ		= 2,

};



static int submit_queues = 1;

module_param(submit_queues, int, S_IRUGO);

MODULE_PARM_DESC(submit_queues, "Number of submission queues");



static int home_node = NUMA_NO_NODE;

module_param(home_node, int, S_IRUGO);

MODULE_PARM_DESC(home_node, "Home node for the device");



static int queue_mode = NULL_Q_MQ;

module_param(queue_mode, int, S_IRUGO);

MODULE_PARM_DESC(use_mq, "Use blk-mq interface (0=bio,1=rq,2=multiqueue)");



static int gb = 250;

module_param(gb, int, S_IRUGO);

MODULE_PARM_DESC(gb, "Size in GB");



static int bs = 512;

module_param(bs, int, S_IRUGO);

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



static int nr_devices = 2;

module_param(nr_devices, int, S_IRUGO);

MODULE_PARM_DESC(nr_devices, "Number of devices to register");



static int irqmode = NULL_IRQ_SOFTIRQ;

module_param(irqmode, int, S_IRUGO);

MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");



static int completion_nsec = 10000;

module_param(completion_nsec, int, S_IRUGO);

MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");



static int hw_queue_depth = 64;

module_param(hw_queue_depth, int, S_IRUGO);

MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");



static bool use_per_node_hctx = true;

module_param(use_per_node_hctx, bool, S_IRUGO);

MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: true");



static void put_tag(struct nullb_queue *nq, unsigned int tag)

{

	clear_bit_unlock(tag, nq->tag_map);



	if (waitqueue_active(&nq->wait))

		wake_up(&nq->wait);

}



static unsigned int get_tag(struct nullb_queue *nq)

{

	unsigned int tag;



	do {

		tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);

		if (tag >= nq->queue_depth)

			return -1U;

	} while (test_and_set_bit_lock(tag, nq->tag_map));



	return tag;

}



static void free_cmd(struct nullb_cmd *cmd)

{

	put_tag(cmd->nq, cmd->tag);

}



static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)

{

	struct nullb_cmd *cmd;

	unsigned int tag;



	tag = get_tag(nq);

	if (tag != -1U) {

		cmd = &nq->cmds[tag];

		cmd->tag = tag;

		cmd->nq = nq;

		return cmd;

	}



	return NULL;

}



static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)

{

	struct nullb_cmd *cmd;

	DEFINE_WAIT(wait);



	cmd = __alloc_cmd(nq);

	if (cmd || !can_wait)

		return cmd;



	do {

		prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);

		cmd = __alloc_cmd(nq);

		if (cmd)

			break;



		io_schedule();

	} while (1);



	finish_wait(&nq->wait, &wait);

	return cmd;

}



static void end_cmd(struct nullb_cmd *cmd)

{

	if (cmd->rq) {

		if (queue_mode == NULL_Q_MQ)

			blk_mq_end_io(cmd->rq, 0);

		else {

			INIT_LIST_HEAD(&cmd->rq->queuelist);

			blk_end_request_all(cmd->rq, 0);

		}

	} else if (cmd->bio)

		bio_endio(cmd->bio, 0);



	if (queue_mode != NULL_Q_MQ)

		free_cmd(cmd);

}



static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)

{

	struct completion_queue *cq;

	struct llist_node *entry;

	struct nullb_cmd *cmd;



	cq = &per_cpu(completion_queues, smp_processor_id());



	while ((entry = llist_del_all(&cq->list)) != NULL) {

		do {

			cmd = container_of(entry, struct nullb_cmd, ll_list);

			end_cmd(cmd);

			entry = entry->next;

		} while (entry);

	}



	return HRTIMER_NORESTART;

}



static void null_cmd_end_timer(struct nullb_cmd *cmd)

{

	struct completion_queue *cq = &per_cpu(completion_queues, get_cpu());



	cmd->ll_list.next = NULL;

	if (llist_add(&cmd->ll_list, &cq->list)) {

		ktime_t kt = ktime_set(0, completion_nsec);



		hrtimer_start(&cq->timer, kt, HRTIMER_MODE_REL);

	}



	put_cpu();

}



static void null_softirq_done_fn(struct request *rq)

{

	blk_end_request_all(rq, 0);

}



#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)



static void null_ipi_cmd_end_io(void *data)

{

	struct completion_queue *cq;

	struct llist_node *entry, *next;

	struct nullb_cmd *cmd;



	cq = &per_cpu(completion_queues, smp_processor_id());



	entry = llist_del_all(&cq->list);



	while (entry) {

		next = entry->next;

		cmd = llist_entry(entry, struct nullb_cmd, ll_list);

		end_cmd(cmd);

		entry = next;

	}

}



static void null_cmd_end_ipi(struct nullb_cmd *cmd)

{

	struct call_single_data *data = &cmd->csd;

	int cpu = get_cpu();

	struct completion_queue *cq = &per_cpu(completion_queues, cpu);



	cmd->ll_list.next = NULL;



	if (llist_add(&cmd->ll_list, &cq->list)) {

		data->func = null_ipi_cmd_end_io;

		data->flags = 0;

		__smp_call_function_single(cpu, data, 0);

	}



	put_cpu();

}



#endif /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */



static inline void null_handle_cmd(struct nullb_cmd *cmd)

{

	/* Complete IO by inline, softirq or timer */

	switch (irqmode) {

	case NULL_IRQ_NONE:

		end_cmd(cmd);

		break;

	case NULL_IRQ_SOFTIRQ:

#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)

		null_cmd_end_ipi(cmd);

#else

		end_cmd(cmd);

#endif

		break;

	case NULL_IRQ_TIMER:

		null_cmd_end_timer(cmd);

		break;

	}

}



static struct nullb_queue *nullb_to_queue(struct nullb *nullb)

{

	int index = 0;



	if (nullb->nr_queues != 1)

		index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);



	return &nullb->queues[index];

}



static void null_queue_bio(struct request_queue *q, struct bio *bio)

{

	struct nullb *nullb = q->queuedata;

	struct nullb_queue *nq = nullb_to_queue(nullb);

	struct nullb_cmd *cmd;



	cmd = alloc_cmd(nq, 1);

	cmd->bio = bio;



	null_handle_cmd(cmd);

}



static int null_rq_prep_fn(struct request_queue *q, struct request *req)

{

	struct nullb *nullb = q->queuedata;

	struct nullb_queue *nq = nullb_to_queue(nullb);

	struct nullb_cmd *cmd;



	cmd = alloc_cmd(nq, 0);

	if (cmd) {

		cmd->rq = req;

		req->special = cmd;

		return BLKPREP_OK;

	}



	return BLKPREP_DEFER;

}



static void null_request_fn(struct request_queue *q)

{

	struct request *rq;



	while ((rq = blk_fetch_request(q)) != NULL) {

		struct nullb_cmd *cmd = rq->special;



		spin_unlock_irq(q->queue_lock);

		null_handle_cmd(cmd);

		spin_lock_irq(q->queue_lock);

	}

}



static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)

{

	struct nullb_cmd *cmd = rq->special;



	cmd->rq = rq;

	cmd->nq = hctx->driver_data;



	null_handle_cmd(cmd);

	return BLK_MQ_RQ_QUEUE_OK;

}



static struct blk_mq_hw_ctx *null_alloc_hctx(struct blk_mq_reg *reg, unsigned int hctx_index)

{

	return kzalloc_node(sizeof(struct blk_mq_hw_ctx), GFP_KERNEL,

				hctx_index);

}



static void null_free_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_index)

{

	kfree(hctx);

}



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];



	init_waitqueue_head(&nq->wait);

	nq->queue_depth = nullb->queue_depth;

	nullb->nr_queues++;

	hctx->driver_data = nq;



	return 0;

}



static struct blk_mq_ops null_mq_ops = {

	.queue_rq       = null_queue_rq,

	.map_queue      = blk_mq_map_queue,

	.init_hctx	= null_init_hctx,

};



static struct blk_mq_reg null_mq_reg = {

	.ops		= &null_mq_ops,

	.queue_depth	= 64,

	.cmd_size	= sizeof(struct nullb_cmd),

	.flags		= BLK_MQ_F_SHOULD_MERGE,

};



static void null_del_dev(struct nullb *nullb)

{

	list_del_init(&nullb->list);



	del_gendisk(nullb->disk);

	if (queue_mode == NULL_Q_MQ)

		blk_mq_free_queue(nullb->q);

	else

		blk_cleanup_queue(nullb->q);

	put_disk(nullb->disk);

	kfree(nullb);

}



static int null_open(struct block_device *bdev, fmode_t mode)

{

	return 0;

}



static void null_release(struct gendisk *disk, fmode_t mode)

{

}



static const struct block_device_operations null_fops = {

	.owner =	THIS_MODULE,

	.open =		null_open,

	.release =	null_release,

};



static int setup_commands(struct nullb_queue *nq)

{

	struct nullb_cmd *cmd;

	int i, tag_size;



	nq->cmds = kzalloc(nq->queue_depth * sizeof(*cmd), GFP_KERNEL);

	if (!nq->cmds)

		return 1;



	tag_size = ALIGN(nq->queue_depth, BITS_PER_LONG) / BITS_PER_LONG;

	nq->tag_map = kzalloc(tag_size * sizeof(unsigned long), GFP_KERNEL);

	if (!nq->tag_map) {

		kfree(nq->cmds);

		return 1;

	}



	for (i = 0; i < nq->queue_depth; i++) {

		cmd = &nq->cmds[i];

		INIT_LIST_HEAD(&cmd->list);

		cmd->ll_list.next = NULL;

		cmd->tag = -1U;

	}



	return 0;

}



static void cleanup_queue(struct nullb_queue *nq)

{

	kfree(nq->tag_map);

	kfree(nq->cmds);

}



static void cleanup_queues(struct nullb *nullb)

{

	int i;



	for (i = 0; i < nullb->nr_queues; i++)

		cleanup_queue(&nullb->queues[i]);



	kfree(nullb->queues);

}



static int setup_queues(struct nullb *nullb)

{

	struct nullb_queue *nq;

	int i;



	nullb->queues = kzalloc(submit_queues * sizeof(*nq), GFP_KERNEL);

	if (!nullb->queues)

		return 1;



	nullb->nr_queues = 0;

	nullb->queue_depth = hw_queue_depth;



	if (queue_mode == NULL_Q_MQ)

		return 0;



	for (i = 0; i < submit_queues; i++) {

		nq = &nullb->queues[i];

		init_waitqueue_head(&nq->wait);

		nq->queue_depth = hw_queue_depth;

		if (setup_commands(nq))

			break;

		nullb->nr_queues++;

	}



	if (i == submit_queues)

		return 0;



	cleanup_queues(nullb);

	return 1;

}



static int null_add_dev(void)

{

	struct gendisk *disk;

	struct nullb *nullb;

	sector_t size;



	nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, home_node);

	if (!nullb)

		return -ENOMEM;



	spin_lock_init(&nullb->lock);



	if (setup_queues(nullb))

		goto err;



	if (queue_mode == NULL_Q_MQ) {

		null_mq_reg.numa_node = home_node;

		null_mq_reg.queue_depth = hw_queue_depth;



		if (use_per_node_hctx) {

			null_mq_reg.ops->alloc_hctx = null_alloc_hctx;

			null_mq_reg.ops->free_hctx = null_free_hctx;



			null_mq_reg.nr_hw_queues = nr_online_nodes;

		} else {

			null_mq_reg.ops->alloc_hctx = blk_mq_alloc_single_hw_queue;

			null_mq_reg.ops->free_hctx = blk_mq_free_single_hw_queue;



			null_mq_reg.nr_hw_queues = submit_queues;

		}



		nullb->q = blk_mq_init_queue(&null_mq_reg, nullb);

	} else if (queue_mode == NULL_Q_BIO) {

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

		blk_queue_make_request(nullb->q, null_queue_bio);

	} else {

		nullb->q = blk_init_queue_node(null_request_fn, &nullb->lock, home_node);

		blk_queue_prep_rq(nullb->q, null_rq_prep_fn);

		if (nullb->q)

			blk_queue_softirq_done(nullb->q, null_softirq_done_fn);

	}



	if (!nullb->q)

		goto queue_fail;



	nullb->q->queuedata = nullb;

	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, nullb->q);



	disk = nullb->disk = alloc_disk_node(1, home_node);

	if (!disk) {

queue_fail:

		if (queue_mode == NULL_Q_MQ)

			blk_mq_free_queue(nullb->q);

		else

			blk_cleanup_queue(nullb->q);

		cleanup_queues(nullb);

err:

		kfree(nullb);

		return -ENOMEM;

	}



	mutex_lock(&lock);

	list_add_tail(&nullb->list, &nullb_list);

	nullb->index = nullb_indexes++;

	mutex_unlock(&lock);



	blk_queue_logical_block_size(nullb->q, bs);

	blk_queue_physical_block_size(nullb->q, bs);



	size = gb * 1024 * 1024 * 1024ULL;

	sector_div(size, bs);

	set_capacity(disk, size);



	disk->flags |= GENHD_FL_EXT_DEVT;

	disk->major		= null_major;

	disk->first_minor	= nullb->index;

	disk->fops		= &null_fops;

	disk->private_data	= nullb;

	disk->queue		= nullb->q;

	sprintf(disk->disk_name, "nullb%d", nullb->index);

	add_disk(disk);

	return 0;

}



static int __init null_init(void)

{

	unsigned int i;



#if !defined(CONFIG_SMP) || !defined(CONFIG_USE_GENERIC_SMP_HELPERS)

	if (irqmode == NULL_IRQ_SOFTIRQ) {

		pr_warn("null_blk: softirq completions not available.\n");

		pr_warn("null_blk: using direct completions.\n");

		irqmode = NULL_IRQ_NONE;

	}

#endif



	if (submit_queues > nr_cpu_ids)

		submit_queues = nr_cpu_ids;

	else if (!submit_queues)

		submit_queues = 1;



	mutex_init(&lock);



	/* Initialize a separate list for each CPU for issuing softirqs */

	for_each_possible_cpu(i) {

		struct completion_queue *cq = &per_cpu(completion_queues, i);



		init_llist_head(&cq->list);



		if (irqmode != NULL_IRQ_TIMER)

			continue;



		hrtimer_init(&cq->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

		cq->timer.function = null_cmd_timer_expired;

	}



	null_major = register_blkdev(0, "nullb");

	if (null_major < 0)

		return null_major;



	for (i = 0; i < nr_devices; i++) {

		if (null_add_dev()) {

			unregister_blkdev(null_major, "nullb");

			return -EINVAL;

		}

	}



	pr_info("null: module loaded\n");

	return 0;

}



static void __exit null_exit(void)

{

	struct nullb *nullb;



	unregister_blkdev(null_major, "nullb");



	mutex_lock(&lock);

	while (!list_empty(&nullb_list)) {

		nullb = list_entry(nullb_list.next, struct nullb, list);

		null_del_dev(nullb);

	}

	mutex_unlock(&lock);

}



module_init(null_init);

module_exit(null_exit);



MODULE_AUTHOR("Jens Axboe <jaxboe@fusionio.com>");

MODULE_LICENSE("GPL");