/*
   * The Kyber I/O scheduler. Controls latency by throttling queue depths using
   * scalable techniques.
   *
   * Copyright (C) 2017 Facebook
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.  If not, see <https://www.gnu.org/licenses/>.
   */
  
  #include <linux/kernel.h>
  #include <linux/blkdev.h>
  #include <linux/blk-mq.h>
  #include <linux/elevator.h>
  #include <linux/module.h>
  #include <linux/sbitmap.h>
  
  #include "blk.h"
  #include "blk-mq.h"

  #include "blk-mq-debugfs.h"

  #include "blk-mq-sched.h"
  #include "blk-mq-tag.h"
  #include "blk-stat.h"
  
  /* Scheduling domains. */
  enum {
  	KYBER_READ,
  	KYBER_SYNC_WRITE,
  	KYBER_OTHER, /* Async writes, discard, etc. */
  	KYBER_NUM_DOMAINS,
  };
  
  enum {
  	KYBER_MIN_DEPTH = 256,
  
  	/*
  	 * In order to prevent starvation of synchronous requests by a flood of
  	 * asynchronous requests, we reserve 25% of requests for synchronous
  	 * operations.
  	 */
  	KYBER_ASYNC_PERCENT = 75,
  };
  
  /*
   * Initial device-wide depths for each scheduling domain.
   *
   * Even for fast devices with lots of tags like NVMe, you can saturate
   * the device with only a fraction of the maximum possible queue depth.
   * So, we cap these to a reasonable value.
   */
  static const unsigned int kyber_depth[] = {
  	[KYBER_READ] = 256,
  	[KYBER_SYNC_WRITE] = 128,
  	[KYBER_OTHER] = 64,
  };
  
  /*
   * Scheduling domain batch sizes. We favor reads.
   */
  static const unsigned int kyber_batch_size[] = {
  	[KYBER_READ] = 16,
  	[KYBER_SYNC_WRITE] = 8,
  	[KYBER_OTHER] = 8,
  };
  
  struct kyber_queue_data {
  	struct request_queue *q;
  
  	struct blk_stat_callback *cb;
  
  	/*
  	 * The device is divided into multiple scheduling domains based on the
  	 * request type. Each domain has a fixed number of in-flight requests of
  	 * that type device-wide, limited by these tokens.
  	 */
  	struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
  
  	/*
  	 * Async request percentage, converted to per-word depth for
  	 * sbitmap_get_shallow().
  	 */
  	unsigned int async_depth;
  
  	/* Target latencies in nanoseconds. */
  	u64 read_lat_nsec, write_lat_nsec;
  };
  
  struct kyber_hctx_data {
  	spinlock_t lock;
  	struct list_head rqs[KYBER_NUM_DOMAINS];
  	unsigned int cur_domain;
  	unsigned int batching;

  	wait_queue_entry_t domain_wait[KYBER_NUM_DOMAINS];

  	atomic_t wait_index[KYBER_NUM_DOMAINS];
  };

  static int rq_sched_domain(const struct request *rq)

  {
  	unsigned int op = rq->cmd_flags;
  
  	if ((op & REQ_OP_MASK) == REQ_OP_READ)
  		return KYBER_READ;
  	else if ((op & REQ_OP_MASK) == REQ_OP_WRITE && op_is_sync(op))
  		return KYBER_SYNC_WRITE;
  	else
  		return KYBER_OTHER;
  }
  
  enum {
  	NONE = 0,
  	GOOD = 1,
  	GREAT = 2,
  	BAD = -1,
  	AWFUL = -2,
  };
  
  #define IS_GOOD(status) ((status) > 0)
  #define IS_BAD(status) ((status) < 0)
  
  static int kyber_lat_status(struct blk_stat_callback *cb,
  			    unsigned int sched_domain, u64 target)
  {
  	u64 latency;
  
  	if (!cb->stat[sched_domain].nr_samples)
  		return NONE;
  
  	latency = cb->stat[sched_domain].mean;
  	if (latency >= 2 * target)
  		return AWFUL;
  	else if (latency > target)
  		return BAD;
  	else if (latency <= target / 2)
  		return GREAT;
  	else /* (latency <= target) */
  		return GOOD;
  }
  
  /*
   * Adjust the read or synchronous write depth given the status of reads and
   * writes. The goal is that the latencies of the two domains are fair (i.e., if
   * one is good, then the other is good).
   */
  static void kyber_adjust_rw_depth(struct kyber_queue_data *kqd,
  				  unsigned int sched_domain, int this_status,
  				  int other_status)
  {
  	unsigned int orig_depth, depth;
  
  	/*
  	 * If this domain had no samples, or reads and writes are both good or
  	 * both bad, don't adjust the depth.
  	 */
  	if (this_status == NONE ||
  	    (IS_GOOD(this_status) && IS_GOOD(other_status)) ||
  	    (IS_BAD(this_status) && IS_BAD(other_status)))
  		return;
  
  	orig_depth = depth = kqd->domain_tokens[sched_domain].sb.depth;
  
  	if (other_status == NONE) {
  		depth++;
  	} else {
  		switch (this_status) {
  		case GOOD:
  			if (other_status == AWFUL)
  				depth -= max(depth / 4, 1U);
  			else
  				depth -= max(depth / 8, 1U);
  			break;
  		case GREAT:
  			if (other_status == AWFUL)
  				depth /= 2;
  			else
  				depth -= max(depth / 4, 1U);
  			break;
  		case BAD:
  			depth++;
  			break;
  		case AWFUL:
  			if (other_status == GREAT)
  				depth += 2;
  			else
  				depth++;
  			break;
  		}
  	}
  
  	depth = clamp(depth, 1U, kyber_depth[sched_domain]);
  	if (depth != orig_depth)
  		sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
  }
  
  /*
   * Adjust the depth of other requests given the status of reads and synchronous
   * writes. As long as either domain is doing fine, we don't throttle, but if
   * both domains are doing badly, we throttle heavily.
   */
  static void kyber_adjust_other_depth(struct kyber_queue_data *kqd,
  				     int read_status, int write_status,
  				     bool have_samples)
  {
  	unsigned int orig_depth, depth;
  	int status;
  
  	orig_depth = depth = kqd->domain_tokens[KYBER_OTHER].sb.depth;
  
  	if (read_status == NONE && write_status == NONE) {
  		depth += 2;
  	} else if (have_samples) {
  		if (read_status == NONE)
  			status = write_status;
  		else if (write_status == NONE)
  			status = read_status;
  		else
  			status = max(read_status, write_status);
  		switch (status) {
  		case GREAT:
  			depth += 2;
  			break;
  		case GOOD:
  			depth++;
  			break;
  		case BAD:
  			depth -= max(depth / 4, 1U);
  			break;
  		case AWFUL:
  			depth /= 2;
  			break;
  		}
  	}
  
  	depth = clamp(depth, 1U, kyber_depth[KYBER_OTHER]);
  	if (depth != orig_depth)
  		sbitmap_queue_resize(&kqd->domain_tokens[KYBER_OTHER], depth);
  }
  
  /*
   * Apply heuristics for limiting queue depths based on gathered latency
   * statistics.
   */
  static void kyber_stat_timer_fn(struct blk_stat_callback *cb)
  {
  	struct kyber_queue_data *kqd = cb->data;
  	int read_status, write_status;
  
  	read_status = kyber_lat_status(cb, KYBER_READ, kqd->read_lat_nsec);
  	write_status = kyber_lat_status(cb, KYBER_SYNC_WRITE, kqd->write_lat_nsec);
  
  	kyber_adjust_rw_depth(kqd, KYBER_READ, read_status, write_status);
  	kyber_adjust_rw_depth(kqd, KYBER_SYNC_WRITE, write_status, read_status);
  	kyber_adjust_other_depth(kqd, read_status, write_status,
  				 cb->stat[KYBER_OTHER].nr_samples != 0);
  
  	/*
  	 * Continue monitoring latencies if we aren't hitting the targets or
  	 * we're still throttling other requests.
  	 */
  	if (!blk_stat_is_active(kqd->cb) &&
  	    ((IS_BAD(read_status) || IS_BAD(write_status) ||
  	      kqd->domain_tokens[KYBER_OTHER].sb.depth < kyber_depth[KYBER_OTHER])))
  		blk_stat_activate_msecs(kqd->cb, 100);
  }
  
  static unsigned int kyber_sched_tags_shift(struct kyber_queue_data *kqd)
  {
  	/*
  	 * All of the hardware queues have the same depth, so we can just grab
  	 * the shift of the first one.
  	 */
  	return kqd->q->queue_hw_ctx[0]->sched_tags->bitmap_tags.sb.shift;
  }
  
  static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
  {
  	struct kyber_queue_data *kqd;
  	unsigned int max_tokens;
  	unsigned int shift;
  	int ret = -ENOMEM;
  	int i;
  
  	kqd = kmalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
  	if (!kqd)
  		goto err;
  	kqd->q = q;
  
  	kqd->cb = blk_stat_alloc_callback(kyber_stat_timer_fn, rq_sched_domain,
  					  KYBER_NUM_DOMAINS, kqd);
  	if (!kqd->cb)
  		goto err_kqd;
  
  	/*
  	 * The maximum number of tokens for any scheduling domain is at least
  	 * the queue depth of a single hardware queue. If the hardware doesn't
  	 * have many tags, still provide a reasonable number.
  	 */
  	max_tokens = max_t(unsigned int, q->tag_set->queue_depth,
  			   KYBER_MIN_DEPTH);
  	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
  		WARN_ON(!kyber_depth[i]);
  		WARN_ON(!kyber_batch_size[i]);
  		ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
  					      max_tokens, -1, false, GFP_KERNEL,
  					      q->node);
  		if (ret) {
  			while (--i >= 0)
  				sbitmap_queue_free(&kqd->domain_tokens[i]);
  			goto err_cb;
  		}
  		sbitmap_queue_resize(&kqd->domain_tokens[i], kyber_depth[i]);
  	}
  
  	shift = kyber_sched_tags_shift(kqd);
  	kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
  
  	kqd->read_lat_nsec = 2000000ULL;
  	kqd->write_lat_nsec = 10000000ULL;
  
  	return kqd;
  
  err_cb:
  	blk_stat_free_callback(kqd->cb);
  err_kqd:
  	kfree(kqd);
  err:
  	return ERR_PTR(ret);
  }
  
  static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)
  {
  	struct kyber_queue_data *kqd;
  	struct elevator_queue *eq;
  
  	eq = elevator_alloc(q, e);
  	if (!eq)
  		return -ENOMEM;
  
  	kqd = kyber_queue_data_alloc(q);
  	if (IS_ERR(kqd)) {
  		kobject_put(&eq->kobj);
  		return PTR_ERR(kqd);
  	}
  
  	eq->elevator_data = kqd;
  	q->elevator = eq;
  
  	blk_stat_add_callback(q, kqd->cb);
  
  	return 0;
  }
  
  static void kyber_exit_sched(struct elevator_queue *e)
  {
  	struct kyber_queue_data *kqd = e->elevator_data;
  	struct request_queue *q = kqd->q;
  	int i;
  
  	blk_stat_remove_callback(q, kqd->cb);
  
  	for (i = 0; i < KYBER_NUM_DOMAINS; i++)
  		sbitmap_queue_free(&kqd->domain_tokens[i]);
  	blk_stat_free_callback(kqd->cb);
  	kfree(kqd);
  }
  
  static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
  {
  	struct kyber_hctx_data *khd;
  	int i;
  
  	khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
  	if (!khd)
  		return -ENOMEM;
  
  	spin_lock_init(&khd->lock);
  
  	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
  		INIT_LIST_HEAD(&khd->rqs[i]);

  		INIT_LIST_HEAD(&khd->domain_wait[i].entry);

  		atomic_set(&khd->wait_index[i], 0);
  	}
  
  	khd->cur_domain = 0;
  	khd->batching = 0;
  
  	hctx->sched_data = khd;
  
  	return 0;
  }
  
  static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
  {
  	kfree(hctx->sched_data);
  }
  
  static int rq_get_domain_token(struct request *rq)
  {
  	return (long)rq->elv.priv[0];
  }
  
  static void rq_set_domain_token(struct request *rq, int token)
  {
  	rq->elv.priv[0] = (void *)(long)token;
  }
  
  static void rq_clear_domain_token(struct kyber_queue_data *kqd,
  				  struct request *rq)
  {
  	unsigned int sched_domain;
  	int nr;
  
  	nr = rq_get_domain_token(rq);
  	if (nr != -1) {
  		sched_domain = rq_sched_domain(rq);
  		sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
  				    rq->mq_ctx->cpu);
  	}
  }

  static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)

  {

  	/*
  	 * We use the scheduler tags as per-hardware queue queueing tokens.
  	 * Async requests can be limited at this stage.
  	 */

  	if (!op_is_sync(op)) {
  		struct kyber_queue_data *kqd = data->q->elevator->elevator_data;

  		data->shallow_depth = kqd->async_depth;

  	}
  }

  static void kyber_prepare_request(struct request *rq, struct bio *bio)
  {
  	rq_set_domain_token(rq, -1);

  }

  static void kyber_finish_request(struct request *rq)

  {

  	struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;

  
  	rq_clear_domain_token(kqd, rq);

  }
  
  static void kyber_completed_request(struct request *rq)
  {
  	struct request_queue *q = rq->q;
  	struct kyber_queue_data *kqd = q->elevator->elevator_data;
  	unsigned int sched_domain;
  	u64 now, latency, target;
  
  	/*
  	 * Check if this request met our latency goal. If not, quickly gather
  	 * some statistics and start throttling.
  	 */
  	sched_domain = rq_sched_domain(rq);
  	switch (sched_domain) {
  	case KYBER_READ:
  		target = kqd->read_lat_nsec;
  		break;
  	case KYBER_SYNC_WRITE:
  		target = kqd->write_lat_nsec;
  		break;
  	default:
  		return;
  	}
  
  	/* If we are already monitoring latencies, don't check again. */
  	if (blk_stat_is_active(kqd->cb))
  		return;
  
  	now = __blk_stat_time(ktime_to_ns(ktime_get()));
  	if (now < blk_stat_time(&rq->issue_stat))
  		return;
  
  	latency = now - blk_stat_time(&rq->issue_stat);
  
  	if (latency > target)
  		blk_stat_activate_msecs(kqd->cb, 10);
  }
  
  static void kyber_flush_busy_ctxs(struct kyber_hctx_data *khd,
  				  struct blk_mq_hw_ctx *hctx)
  {
  	LIST_HEAD(rq_list);
  	struct request *rq, *next;
  
  	blk_mq_flush_busy_ctxs(hctx, &rq_list);
  	list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
  		unsigned int sched_domain;
  
  		sched_domain = rq_sched_domain(rq);
  		list_move_tail(&rq->queuelist, &khd->rqs[sched_domain]);
  	}
  }

  static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,

  			     void *key)
  {
  	struct blk_mq_hw_ctx *hctx = READ_ONCE(wait->private);

  	list_del_init(&wait->entry);

  	blk_mq_run_hw_queue(hctx, true);
  	return 1;
  }
  
  static int kyber_get_domain_token(struct kyber_queue_data *kqd,
  				  struct kyber_hctx_data *khd,
  				  struct blk_mq_hw_ctx *hctx)
  {
  	unsigned int sched_domain = khd->cur_domain;
  	struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];

  	wait_queue_entry_t *wait = &khd->domain_wait[sched_domain];

  	struct sbq_wait_state *ws;
  	int nr;
  
  	nr = __sbitmap_queue_get(domain_tokens);
  	if (nr >= 0)
  		return nr;
  
  	/*
  	 * If we failed to get a domain token, make sure the hardware queue is
  	 * run when one becomes available. Note that this is serialized on
  	 * khd->lock, but we still need to be careful about the waker.
  	 */

  	if (list_empty_careful(&wait->entry)) {

  		init_waitqueue_func_entry(wait, kyber_domain_wake);
  		wait->private = hctx;
  		ws = sbq_wait_ptr(domain_tokens,
  				  &khd->wait_index[sched_domain]);
  		add_wait_queue(&ws->wait, wait);
  
  		/*
  		 * Try again in case a token was freed before we got on the wait
  		 * queue.
  		 */
  		nr = __sbitmap_queue_get(domain_tokens);
  	}
  	return nr;
  }
  
  static struct request *
  kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
  			  struct kyber_hctx_data *khd,
  			  struct blk_mq_hw_ctx *hctx,
  			  bool *flushed)
  {
  	struct list_head *rqs;
  	struct request *rq;
  	int nr;
  
  	rqs = &khd->rqs[khd->cur_domain];
  	rq = list_first_entry_or_null(rqs, struct request, queuelist);
  
  	/*
  	 * If there wasn't already a pending request and we haven't flushed the
  	 * software queues yet, flush the software queues and check again.
  	 */
  	if (!rq && !*flushed) {
  		kyber_flush_busy_ctxs(khd, hctx);
  		*flushed = true;
  		rq = list_first_entry_or_null(rqs, struct request, queuelist);
  	}
  
  	if (rq) {
  		nr = kyber_get_domain_token(kqd, khd, hctx);
  		if (nr >= 0) {
  			khd->batching++;
  			rq_set_domain_token(rq, nr);
  			list_del_init(&rq->queuelist);
  			return rq;
  		}
  	}
  
  	/* There were either no pending requests or no tokens. */
  	return NULL;
  }
  
  static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
  {
  	struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
  	struct kyber_hctx_data *khd = hctx->sched_data;
  	bool flushed = false;
  	struct request *rq;
  	int i;
  
  	spin_lock(&khd->lock);
  
  	/*
  	 * First, if we are still entitled to batch, try to dispatch a request
  	 * from the batch.
  	 */
  	if (khd->batching < kyber_batch_size[khd->cur_domain]) {
  		rq = kyber_dispatch_cur_domain(kqd, khd, hctx, &flushed);
  		if (rq)
  			goto out;
  	}
  
  	/*
  	 * Either,
  	 * 1. We were no longer entitled to a batch.
  	 * 2. The domain we were batching didn't have any requests.
  	 * 3. The domain we were batching was out of tokens.
  	 *
  	 * Start another batch. Note that this wraps back around to the original
  	 * domain if no other domains have requests or tokens.
  	 */
  	khd->batching = 0;
  	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
  		if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
  			khd->cur_domain = 0;
  		else
  			khd->cur_domain++;
  
  		rq = kyber_dispatch_cur_domain(kqd, khd, hctx, &flushed);
  		if (rq)
  			goto out;
  	}
  
  	rq = NULL;
  out:
  	spin_unlock(&khd->lock);
  	return rq;
  }
  
  static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
  {
  	struct kyber_hctx_data *khd = hctx->sched_data;
  	int i;
  
  	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
  		if (!list_empty_careful(&khd->rqs[i]))
  			return true;
  	}
  	return false;
  }
  
  #define KYBER_LAT_SHOW_STORE(op)					\
  static ssize_t kyber_##op##_lat_show(struct elevator_queue *e,		\
  				     char *page)			\
  {									\
  	struct kyber_queue_data *kqd = e->elevator_data;		\
  									\
  	return sprintf(page, "%llu
  ", kqd->op##_lat_nsec);		\
  }									\
  									\
  static ssize_t kyber_##op##_lat_store(struct elevator_queue *e,		\
  				      const char *page, size_t count)	\
  {									\
  	struct kyber_queue_data *kqd = e->elevator_data;		\
  	unsigned long long nsec;					\
  	int ret;							\
  									\
  	ret = kstrtoull(page, 10, &nsec);				\
  	if (ret)							\
  		return ret;						\
  									\
  	kqd->op##_lat_nsec = nsec;					\
  									\
  	return count;							\
  }
  KYBER_LAT_SHOW_STORE(read);
  KYBER_LAT_SHOW_STORE(write);
  #undef KYBER_LAT_SHOW_STORE
  
  #define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
  static struct elv_fs_entry kyber_sched_attrs[] = {
  	KYBER_LAT_ATTR(read),
  	KYBER_LAT_ATTR(write),
  	__ATTR_NULL
  };
  #undef KYBER_LAT_ATTR

  #ifdef CONFIG_BLK_DEBUG_FS
  #define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name)			\
  static int kyber_##name##_tokens_show(void *data, struct seq_file *m)	\
  {									\
  	struct request_queue *q = data;					\
  	struct kyber_queue_data *kqd = q->elevator->elevator_data;	\
  									\
  	sbitmap_queue_show(&kqd->domain_tokens[domain], m);		\
  	return 0;							\
  }									\
  									\
  static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos)	\
  	__acquires(&khd->lock)						\
  {									\
  	struct blk_mq_hw_ctx *hctx = m->private;			\
  	struct kyber_hctx_data *khd = hctx->sched_data;			\
  									\
  	spin_lock(&khd->lock);						\
  	return seq_list_start(&khd->rqs[domain], *pos);			\
  }									\
  									\
  static void *kyber_##name##_rqs_next(struct seq_file *m, void *v,	\
  				     loff_t *pos)			\
  {									\
  	struct blk_mq_hw_ctx *hctx = m->private;			\
  	struct kyber_hctx_data *khd = hctx->sched_data;			\
  									\
  	return seq_list_next(v, &khd->rqs[domain], pos);		\
  }									\
  									\
  static void kyber_##name##_rqs_stop(struct seq_file *m, void *v)	\
  	__releases(&khd->lock)						\
  {									\
  	struct blk_mq_hw_ctx *hctx = m->private;			\
  	struct kyber_hctx_data *khd = hctx->sched_data;			\
  									\
  	spin_unlock(&khd->lock);					\
  }									\
  									\
  static const struct seq_operations kyber_##name##_rqs_seq_ops = {	\
  	.start	= kyber_##name##_rqs_start,				\
  	.next	= kyber_##name##_rqs_next,				\
  	.stop	= kyber_##name##_rqs_stop,				\
  	.show	= blk_mq_debugfs_rq_show,				\
  };									\
  									\
  static int kyber_##name##_waiting_show(void *data, struct seq_file *m)	\
  {									\
  	struct blk_mq_hw_ctx *hctx = data;				\
  	struct kyber_hctx_data *khd = hctx->sched_data;			\

  	wait_queue_entry_t *wait = &khd->domain_wait[domain];		\

  									\

  	seq_printf(m, "%d
  ", !list_empty_careful(&wait->entry));	\

  	return 0;							\
  }
  KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
  KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_SYNC_WRITE, sync_write)
  KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
  #undef KYBER_DEBUGFS_DOMAIN_ATTRS
  
  static int kyber_async_depth_show(void *data, struct seq_file *m)
  {
  	struct request_queue *q = data;
  	struct kyber_queue_data *kqd = q->elevator->elevator_data;
  
  	seq_printf(m, "%u
  ", kqd->async_depth);
  	return 0;
  }
  
  static int kyber_cur_domain_show(void *data, struct seq_file *m)
  {
  	struct blk_mq_hw_ctx *hctx = data;
  	struct kyber_hctx_data *khd = hctx->sched_data;
  
  	switch (khd->cur_domain) {
  	case KYBER_READ:
  		seq_puts(m, "READ
  ");
  		break;
  	case KYBER_SYNC_WRITE:
  		seq_puts(m, "SYNC_WRITE
  ");
  		break;
  	case KYBER_OTHER:
  		seq_puts(m, "OTHER
  ");
  		break;
  	default:
  		seq_printf(m, "%u
  ", khd->cur_domain);
  		break;
  	}
  	return 0;
  }
  
  static int kyber_batching_show(void *data, struct seq_file *m)
  {
  	struct blk_mq_hw_ctx *hctx = data;
  	struct kyber_hctx_data *khd = hctx->sched_data;
  
  	seq_printf(m, "%u
  ", khd->batching);
  	return 0;
  }
  
  #define KYBER_QUEUE_DOMAIN_ATTRS(name)	\
  	{#name "_tokens", 0400, kyber_##name##_tokens_show}
  static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
  	KYBER_QUEUE_DOMAIN_ATTRS(read),
  	KYBER_QUEUE_DOMAIN_ATTRS(sync_write),
  	KYBER_QUEUE_DOMAIN_ATTRS(other),
  	{"async_depth", 0400, kyber_async_depth_show},
  	{},
  };
  #undef KYBER_QUEUE_DOMAIN_ATTRS
  
  #define KYBER_HCTX_DOMAIN_ATTRS(name)					\
  	{#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops},	\
  	{#name "_waiting", 0400, kyber_##name##_waiting_show}
  static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
  	KYBER_HCTX_DOMAIN_ATTRS(read),
  	KYBER_HCTX_DOMAIN_ATTRS(sync_write),
  	KYBER_HCTX_DOMAIN_ATTRS(other),
  	{"cur_domain", 0400, kyber_cur_domain_show},
  	{"batching", 0400, kyber_batching_show},
  	{},
  };
  #undef KYBER_HCTX_DOMAIN_ATTRS
  #endif

  static struct elevator_type kyber_sched = {
  	.ops.mq = {
  		.init_sched = kyber_init_sched,
  		.exit_sched = kyber_exit_sched,
  		.init_hctx = kyber_init_hctx,
  		.exit_hctx = kyber_exit_hctx,

  		.limit_depth = kyber_limit_depth,
  		.prepare_request = kyber_prepare_request,

  		.finish_request = kyber_finish_request,

  		.requeue_request = kyber_finish_request,

  		.completed_request = kyber_completed_request,
  		.dispatch_request = kyber_dispatch_request,
  		.has_work = kyber_has_work,
  	},
  	.uses_mq = true,

  #ifdef CONFIG_BLK_DEBUG_FS
  	.queue_debugfs_attrs = kyber_queue_debugfs_attrs,
  	.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
  #endif

  	.elevator_attrs = kyber_sched_attrs,
  	.elevator_name = "kyber",
  	.elevator_owner = THIS_MODULE,
  };
  
  static int __init kyber_init(void)
  {
  	return elv_register(&kyber_sched);
  }
  
  static void __exit kyber_exit(void)
  {
  	elv_unregister(&kyber_sched);
  }
  
  module_init(kyber_init);
  module_exit(kyber_exit);
  
  MODULE_AUTHOR("Omar Sandoval");
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("Kyber I/O scheduler");