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: Jens Axboe <axboe@kernel.dk>
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@ -35,7 +35,8 @@ struct nullb {
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struct request_queue *q;
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struct gendisk *disk;
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struct nvm_dev *ndev;
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struct blk_mq_tag_set tag_set;
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struct blk_mq_tag_set *tag_set;
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struct blk_mq_tag_set __tag_set;
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struct hrtimer timer;
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unsigned int queue_depth;
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spinlock_t lock;
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@ -50,6 +51,7 @@ static struct mutex lock;
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static int null_major;
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static int nullb_indexes;
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static struct kmem_cache *ppa_cache;
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static struct blk_mq_tag_set tag_set;
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enum {
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NULL_IRQ_NONE = 0,
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@ -109,7 +111,7 @@ static int bs = 512;
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module_param(bs, int, S_IRUGO);
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MODULE_PARM_DESC(bs, "Block size (in bytes)");
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static int nr_devices = 2;
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static int nr_devices = 1;
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module_param(nr_devices, int, S_IRUGO);
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MODULE_PARM_DESC(nr_devices, "Number of devices to register");
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@ -121,6 +123,10 @@ static bool blocking;
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module_param(blocking, bool, S_IRUGO);
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MODULE_PARM_DESC(blocking, "Register as a blocking blk-mq driver device");
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static bool shared_tags;
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module_param(shared_tags, bool, S_IRUGO);
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MODULE_PARM_DESC(shared_tags, "Share tag set between devices for blk-mq");
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static int irqmode = NULL_IRQ_SOFTIRQ;
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static int null_set_irqmode(const char *str, const struct kernel_param *kp)
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@ -376,31 +382,8 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
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return BLK_STS_OK;
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}
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static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
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{
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BUG_ON(!nullb);
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BUG_ON(!nq);
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init_waitqueue_head(&nq->wait);
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nq->queue_depth = nullb->queue_depth;
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}
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static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
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unsigned int index)
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{
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struct nullb *nullb = data;
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struct nullb_queue *nq = &nullb->queues[index];
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hctx->driver_data = nq;
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null_init_queue(nullb, nq);
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nullb->nr_queues++;
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return 0;
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}
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static const struct blk_mq_ops null_mq_ops = {
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.queue_rq = null_queue_rq,
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.init_hctx = null_init_hctx,
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.complete = null_softirq_done_fn,
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};
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@ -592,8 +575,8 @@ static void null_del_dev(struct nullb *nullb)
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else
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del_gendisk(nullb->disk);
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blk_cleanup_queue(nullb->q);
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if (queue_mode == NULL_Q_MQ)
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blk_mq_free_tag_set(&nullb->tag_set);
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if (queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)
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blk_mq_free_tag_set(nullb->tag_set);
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if (!use_lightnvm)
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put_disk(nullb->disk);
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cleanup_queues(nullb);
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@ -615,6 +598,32 @@ static const struct block_device_operations null_fops = {
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.release = null_release,
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};
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static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
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{
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BUG_ON(!nullb);
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BUG_ON(!nq);
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init_waitqueue_head(&nq->wait);
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nq->queue_depth = nullb->queue_depth;
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}
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static void null_init_queues(struct nullb *nullb)
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{
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struct request_queue *q = nullb->q;
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struct blk_mq_hw_ctx *hctx;
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struct nullb_queue *nq;
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int i;
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queue_for_each_hw_ctx(q, hctx, i) {
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if (!hctx->nr_ctx || !hctx->tags)
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continue;
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nq = &nullb->queues[i];
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hctx->driver_data = nq;
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null_init_queue(nullb, nq);
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nullb->nr_queues++;
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}
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}
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static int setup_commands(struct nullb_queue *nq)
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{
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struct nullb_cmd *cmd;
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@ -695,6 +704,22 @@ static int null_gendisk_register(struct nullb *nullb)
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return 0;
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}
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static int null_init_tag_set(struct blk_mq_tag_set *set)
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{
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set->ops = &null_mq_ops;
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set->nr_hw_queues = submit_queues;
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set->queue_depth = hw_queue_depth;
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set->numa_node = home_node;
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set->cmd_size = sizeof(struct nullb_cmd);
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set->flags = BLK_MQ_F_SHOULD_MERGE;
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set->driver_data = NULL;
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if (blocking)
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set->flags |= BLK_MQ_F_BLOCKING;
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return blk_mq_alloc_tag_set(set);
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}
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static int null_add_dev(void)
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{
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struct nullb *nullb;
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@ -716,26 +741,23 @@ static int null_add_dev(void)
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goto out_free_nullb;
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if (queue_mode == NULL_Q_MQ) {
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nullb->tag_set.ops = &null_mq_ops;
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nullb->tag_set.nr_hw_queues = submit_queues;
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nullb->tag_set.queue_depth = hw_queue_depth;
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nullb->tag_set.numa_node = home_node;
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nullb->tag_set.cmd_size = sizeof(struct nullb_cmd);
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nullb->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
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nullb->tag_set.driver_data = nullb;
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if (shared_tags) {
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nullb->tag_set = &tag_set;
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rv = 0;
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} else {
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nullb->tag_set = &nullb->__tag_set;
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rv = null_init_tag_set(nullb->tag_set);
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}
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if (blocking)
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nullb->tag_set.flags |= BLK_MQ_F_BLOCKING;
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rv = blk_mq_alloc_tag_set(&nullb->tag_set);
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if (rv)
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goto out_cleanup_queues;
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nullb->q = blk_mq_init_queue(&nullb->tag_set);
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nullb->q = blk_mq_init_queue(nullb->tag_set);
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if (IS_ERR(nullb->q)) {
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rv = -ENOMEM;
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goto out_cleanup_tags;
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}
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null_init_queues(nullb);
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} else if (queue_mode == NULL_Q_BIO) {
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nullb->q = blk_alloc_queue_node(GFP_KERNEL, home_node);
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if (!nullb->q) {
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@ -788,8 +810,8 @@ static int null_add_dev(void)
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out_cleanup_blk_queue:
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blk_cleanup_queue(nullb->q);
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out_cleanup_tags:
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if (queue_mode == NULL_Q_MQ)
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blk_mq_free_tag_set(&nullb->tag_set);
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if (queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)
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blk_mq_free_tag_set(nullb->tag_set);
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out_cleanup_queues:
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cleanup_queues(nullb);
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out_free_nullb:
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@ -822,6 +844,9 @@ static int __init null_init(void)
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queue_mode = NULL_Q_MQ;
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}
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if (queue_mode == NULL_Q_MQ && shared_tags)
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null_init_tag_set(&tag_set);
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if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {
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if (submit_queues < nr_online_nodes) {
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pr_warn("null_blk: submit_queues param is set to %u.",
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@ -882,6 +907,9 @@ static void __exit null_exit(void)
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}
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mutex_unlock(&lock);
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if (queue_mode == NULL_Q_MQ && shared_tags)
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blk_mq_free_tag_set(&tag_set);
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kmem_cache_destroy(ppa_cache);
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}
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