/*
   * Functions related to sysfs handling
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/bio.h>
  #include <linux/blkdev.h>
  #include <linux/blktrace_api.h>
  
  #include "blk.h"
  
  struct queue_sysfs_entry {
  	struct attribute attr;
  	ssize_t (*show)(struct request_queue *, char *);
  	ssize_t (*store)(struct request_queue *, const char *, size_t);
  };
  
  static ssize_t
  queue_var_show(unsigned int var, char *page)
  {
  	return sprintf(page, "%d
  ", var);
  }
  
  static ssize_t
  queue_var_store(unsigned long *var, const char *page, size_t count)
  {
  	char *p = (char *) page;
  
  	*var = simple_strtoul(p, &p, 10);
  	return count;
  }
  
  static ssize_t queue_requests_show(struct request_queue *q, char *page)
  {
  	return queue_var_show(q->nr_requests, (page));
  }
  
  static ssize_t
  queue_requests_store(struct request_queue *q, const char *page, size_t count)
  {
  	struct request_list *rl = &q->rq;
  	unsigned long nr;
  	int ret = queue_var_store(&nr, page, count);
  	if (nr < BLKDEV_MIN_RQ)
  		nr = BLKDEV_MIN_RQ;
  
  	spin_lock_irq(q->queue_lock);
  	q->nr_requests = nr;
  	blk_queue_congestion_threshold(q);
  
  	if (rl->count[READ] >= queue_congestion_on_threshold(q))
  		blk_set_queue_congested(q, READ);
  	else if (rl->count[READ] < queue_congestion_off_threshold(q))
  		blk_clear_queue_congested(q, READ);
  
  	if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
  		blk_set_queue_congested(q, WRITE);
  	else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
  		blk_clear_queue_congested(q, WRITE);
  
  	if (rl->count[READ] >= q->nr_requests) {
  		blk_set_queue_full(q, READ);
  	} else if (rl->count[READ]+1 <= q->nr_requests) {
  		blk_clear_queue_full(q, READ);
  		wake_up(&rl->wait[READ]);
  	}
  
  	if (rl->count[WRITE] >= q->nr_requests) {
  		blk_set_queue_full(q, WRITE);
  	} else if (rl->count[WRITE]+1 <= q->nr_requests) {
  		blk_clear_queue_full(q, WRITE);
  		wake_up(&rl->wait[WRITE]);
  	}
  	spin_unlock_irq(q->queue_lock);
  	return ret;
  }
  
  static ssize_t queue_ra_show(struct request_queue *q, char *page)
  {
  	int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
  
  	return queue_var_show(ra_kb, (page));
  }
  
  static ssize_t
  queue_ra_store(struct request_queue *q, const char *page, size_t count)
  {
  	unsigned long ra_kb;
  	ssize_t ret = queue_var_store(&ra_kb, page, count);
  
  	spin_lock_irq(q->queue_lock);
  	q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
  	spin_unlock_irq(q->queue_lock);
  
  	return ret;
  }
  
  static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
  {
  	int max_sectors_kb = q->max_sectors >> 1;
  
  	return queue_var_show(max_sectors_kb, (page));
  }

  static ssize_t queue_hw_sector_size_show(struct request_queue *q, char *page)
  {
  	return queue_var_show(q->hardsect_size, page);
  }

  static ssize_t
  queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
  {
  	unsigned long max_sectors_kb,
  			max_hw_sectors_kb = q->max_hw_sectors >> 1,
  			page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
  	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
  
  	if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
  		return -EINVAL;
  	/*
  	 * Take the queue lock to update the readahead and max_sectors
  	 * values synchronously:
  	 */
  	spin_lock_irq(q->queue_lock);
  	q->max_sectors = max_sectors_kb << 1;
  	spin_unlock_irq(q->queue_lock);
  
  	return ret;
  }
  
  static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
  {
  	int max_hw_sectors_kb = q->max_hw_sectors >> 1;
  
  	return queue_var_show(max_hw_sectors_kb, (page));
  }

  static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
  {
  	return queue_var_show(blk_queue_nomerges(q), page);
  }
  
  static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
  				    size_t count)
  {
  	unsigned long nm;
  	ssize_t ret = queue_var_store(&nm, page, count);

  	spin_lock_irq(q->queue_lock);

  	if (nm)

  		queue_flag_set(QUEUE_FLAG_NOMERGES, q);

  	else

  		queue_flag_clear(QUEUE_FLAG_NOMERGES, q);

  	spin_unlock_irq(q->queue_lock);

  	return ret;
  }

  
  static struct queue_sysfs_entry queue_requests_entry = {
  	.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
  	.show = queue_requests_show,
  	.store = queue_requests_store,
  };
  
  static struct queue_sysfs_entry queue_ra_entry = {
  	.attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
  	.show = queue_ra_show,
  	.store = queue_ra_store,
  };
  
  static struct queue_sysfs_entry queue_max_sectors_entry = {
  	.attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
  	.show = queue_max_sectors_show,
  	.store = queue_max_sectors_store,
  };
  
  static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
  	.attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
  	.show = queue_max_hw_sectors_show,
  };
  
  static struct queue_sysfs_entry queue_iosched_entry = {
  	.attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
  	.show = elv_iosched_show,
  	.store = elv_iosched_store,
  };

  static struct queue_sysfs_entry queue_hw_sector_size_entry = {
  	.attr = {.name = "hw_sector_size", .mode = S_IRUGO },
  	.show = queue_hw_sector_size_show,
  };

  static struct queue_sysfs_entry queue_nomerges_entry = {
  	.attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
  	.show = queue_nomerges_show,
  	.store = queue_nomerges_store,
  };

  static struct attribute *default_attrs[] = {
  	&queue_requests_entry.attr,
  	&queue_ra_entry.attr,
  	&queue_max_hw_sectors_entry.attr,
  	&queue_max_sectors_entry.attr,
  	&queue_iosched_entry.attr,

  	&queue_hw_sector_size_entry.attr,

  	&queue_nomerges_entry.attr,

  	NULL,
  };
  
  #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
  
  static ssize_t
  queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
  {
  	struct queue_sysfs_entry *entry = to_queue(attr);
  	struct request_queue *q =
  		container_of(kobj, struct request_queue, kobj);
  	ssize_t res;
  
  	if (!entry->show)
  		return -EIO;
  	mutex_lock(&q->sysfs_lock);
  	if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
  		mutex_unlock(&q->sysfs_lock);
  		return -ENOENT;
  	}
  	res = entry->show(q, page);
  	mutex_unlock(&q->sysfs_lock);
  	return res;
  }
  
  static ssize_t
  queue_attr_store(struct kobject *kobj, struct attribute *attr,
  		    const char *page, size_t length)
  {
  	struct queue_sysfs_entry *entry = to_queue(attr);

  	struct request_queue *q;

  	ssize_t res;
  
  	if (!entry->store)
  		return -EIO;

  
  	q = container_of(kobj, struct request_queue, kobj);

  	mutex_lock(&q->sysfs_lock);
  	if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
  		mutex_unlock(&q->sysfs_lock);
  		return -ENOENT;
  	}
  	res = entry->store(q, page, length);
  	mutex_unlock(&q->sysfs_lock);
  	return res;
  }
  
  /**
   * blk_cleanup_queue: - release a &struct request_queue when it is no longer needed
   * @kobj:    the kobj belonging of the request queue to be released
   *
   * Description:
   *     blk_cleanup_queue is the pair to blk_init_queue() or
   *     blk_queue_make_request().  It should be called when a request queue is
   *     being released; typically when a block device is being de-registered.
   *     Currently, its primary task it to free all the &struct request
   *     structures that were allocated to the queue and the queue itself.
   *
   * Caveat:
   *     Hopefully the low level driver will have finished any
   *     outstanding requests first...
   **/
  static void blk_release_queue(struct kobject *kobj)
  {
  	struct request_queue *q =
  		container_of(kobj, struct request_queue, kobj);
  	struct request_list *rl = &q->rq;
  
  	blk_sync_queue(q);
  
  	if (rl->rq_pool)
  		mempool_destroy(rl->rq_pool);
  
  	if (q->queue_tags)
  		__blk_queue_free_tags(q);
  
  	blk_trace_shutdown(q);
  
  	bdi_destroy(&q->backing_dev_info);
  	kmem_cache_free(blk_requestq_cachep, q);
  }
  
  static struct sysfs_ops queue_sysfs_ops = {
  	.show	= queue_attr_show,
  	.store	= queue_attr_store,
  };
  
  struct kobj_type blk_queue_ktype = {
  	.sysfs_ops	= &queue_sysfs_ops,
  	.default_attrs	= default_attrs,
  	.release	= blk_release_queue,
  };
  
  int blk_register_queue(struct gendisk *disk)
  {
  	int ret;
  
  	struct request_queue *q = disk->queue;

  	if (WARN_ON(!q))

  		return -ENXIO;

  	if (!q->request_fn)
  		return 0;

  	ret = kobject_add(&q->kobj, kobject_get(&disk->dev.kobj),
  			  "%s", "queue");
  	if (ret < 0)
  		return ret;
  
  	kobject_uevent(&q->kobj, KOBJ_ADD);
  
  	ret = elv_register_queue(q);
  	if (ret) {
  		kobject_uevent(&q->kobj, KOBJ_REMOVE);
  		kobject_del(&q->kobj);
  		return ret;
  	}
  
  	return 0;
  }
  
  void blk_unregister_queue(struct gendisk *disk)
  {
  	struct request_queue *q = disk->queue;

  	if (WARN_ON(!q))
  		return;
  
  	if (q->request_fn) {

  		elv_unregister_queue(q);
  
  		kobject_uevent(&q->kobj, KOBJ_REMOVE);
  		kobject_del(&q->kobj);
  		kobject_put(&disk->dev.kobj);
  	}
  }