/*
   * Functions related to generic timeout handling of requests.
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/blkdev.h>

  #include <linux/fault-inject.h>

  
  #include "blk.h"

  #include "blk-mq.h"

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  
  static DECLARE_FAULT_ATTR(fail_io_timeout);
  
  static int __init setup_fail_io_timeout(char *str)
  {
  	return setup_fault_attr(&fail_io_timeout, str);
  }
  __setup("fail_io_timeout=", setup_fail_io_timeout);
  
  int blk_should_fake_timeout(struct request_queue *q)
  {
  	if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
  		return 0;
  
  	return should_fail(&fail_io_timeout, 1);
  }
  
  static int __init fail_io_timeout_debugfs(void)
  {

  	struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
  						NULL, &fail_io_timeout);

  	return PTR_ERR_OR_ZERO(dir);

  }
  
  late_initcall(fail_io_timeout_debugfs);
  
  ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
  			  char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  	int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
  
  	return sprintf(buf, "%d
  ", set != 0);
  }
  
  ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
  			   const char *buf, size_t count)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  	int val;
  
  	if (count) {
  		struct request_queue *q = disk->queue;
  		char *p = (char *) buf;
  
  		val = simple_strtoul(p, &p, 10);

  		if (val)

  			blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);

  		else

  			blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);

  	}
  
  	return count;
  }
  
  #endif /* CONFIG_FAIL_IO_TIMEOUT */

  /*
   * blk_delete_timer - Delete/cancel timer for a given function.
   * @req:	request that we are canceling timer for
   *
   */
  void blk_delete_timer(struct request *req)
  {

  	list_del_init(&req->timeout_list);

  }
  
  static void blk_rq_timed_out(struct request *req)
  {
  	struct request_queue *q = req->q;

  	enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;

  	if (q->rq_timed_out_fn)
  		ret = q->rq_timed_out_fn(req);

  	switch (ret) {

  	case BLK_EH_RESET_TIMER:

  		blk_add_timer(req);

  		blk_clear_rq_complete(req);

  		break;

  	case BLK_EH_DONE:

  		/*
  		 * LLD handles this for now but in the future
  		 * we can send a request msg to abort the command
  		 * and we can move more of the generic scsi eh code to
  		 * the blk layer.
  		 */
  		break;
  	default:
  		printk(KERN_ERR "block: bad eh return: %d
  ", ret);
  		break;
  	}
  }

  static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,

  			  unsigned int *next_set)
  {

  	const unsigned long deadline = blk_rq_deadline(rq);
  
  	if (time_after_eq(jiffies, deadline)) {

  		list_del_init(&rq->timeout_list);
  
  		/*
  		 * Check if we raced with end io completion
  		 */
  		if (!blk_mark_rq_complete(rq))
  			blk_rq_timed_out(rq);

  	} else if (!*next_set || time_after(*next_timeout, deadline)) {
  		*next_timeout = deadline;

  		*next_set = 1;
  	}
  }

  void blk_timeout_work(struct work_struct *work)

  {

  	struct request_queue *q =
  		container_of(work, struct request_queue, timeout_work);

  	unsigned long flags, next = 0;

  	struct request *rq, *tmp;

  	int next_set = 0;

  
  	spin_lock_irqsave(q->queue_lock, flags);

  	list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
  		blk_rq_check_expired(rq, &next, &next_set);

  	if (next_set)

  		mod_timer(&q->timeout, round_jiffies_up(next));

  
  	spin_unlock_irqrestore(q->queue_lock, flags);
  }
  
  /**
   * blk_abort_request -- Request request recovery for the specified command
   * @req:	pointer to the request of interest
   *
   * This function requests that the block layer start recovery for the
   * request by deleting the timer and calling the q's timeout function.
   * LLDDs who implement their own error recovery MAY ignore the timeout
   * event if they generated blk_abort_req. Must hold queue lock.
   */
  void blk_abort_request(struct request *req)
  {

  	if (req->q->mq_ops) {

  		/*
  		 * All we need to ensure is that timeout scan takes place
  		 * immediately and that scan sees the new timeout value.
  		 * No need for fancy synchronizations.
  		 */

  		blk_rq_set_deadline(req, jiffies);

  		kblockd_schedule_work(&req->q->timeout_work);

  	} else {

  		if (blk_mark_rq_complete(req))
  			return;

  		blk_delete_timer(req);

  		blk_rq_timed_out(req);

  	}

  }
  EXPORT_SYMBOL_GPL(blk_abort_request);

  unsigned long blk_rq_timeout(unsigned long timeout)
  {
  	unsigned long maxt;
  
  	maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
  	if (time_after(timeout, maxt))
  		timeout = maxt;
  
  	return timeout;
  }

  /**
   * blk_add_timer - Start timeout timer for a single request
   * @req:	request that is about to start running.
   *
   * Notes:
   *    Each request has its own timer, and as it is added to the queue, we
   *    set up the timer. When the request completes, we cancel the timer.
   */
  void blk_add_timer(struct request *req)

  {
  	struct request_queue *q = req->q;
  	unsigned long expiry;

  	if (!q->mq_ops)
  		lockdep_assert_held(q->queue_lock);

  	/* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
  	if (!q->mq_ops && !q->rq_timed_out_fn)

  		return;
  
  	BUG_ON(!list_empty(&req->timeout_list));

  	/*
  	 * Some LLDs, like scsi, peek at the timeout to prevent a
  	 * command from being retried forever.
  	 */
  	if (!req->timeout)

  		req->timeout = q->rq_timeout;

  	req->rq_flags &= ~RQF_TIMED_OUT;

  	blk_rq_set_deadline(req, jiffies + req->timeout);

  
  	/*
  	 * Only the non-mq case needs to add the request to a protected list.
  	 * For the mq case we simply scan the tag map.
  	 */

  	if (!q->mq_ops)
  		list_add_tail(&req->timeout_list, &req->q->timeout_list);

  
  	/*
  	 * If the timer isn't already pending or this timeout is earlier

  	 * than an existing one, modify the timer. Round up to next nearest

  	 * second.
  	 */

  	expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));

  
  	if (!timer_pending(&q->timeout) ||

  	    time_before(expiry, q->timeout.expires)) {
  		unsigned long diff = q->timeout.expires - expiry;
  
  		/*
  		 * Due to added timer slack to group timers, the timer
  		 * will often be a little in front of what we asked for.
  		 * So apply some tolerance here too, otherwise we keep
  		 * modifying the timer because expires for value X
  		 * will be X + something.
  		 */

  		if (!timer_pending(&q->timeout) || (diff >= HZ / 2))

  			mod_timer(&q->timeout, expiry);
  	}

  
  }