--- /dev/null
+#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");
projects / ~andy / linux / commitdiff