text: /*
   * 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"
  
  #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 IS_ERR(dir) ? PTR_ERR(dir) : 0;
  }
  
  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\n", 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);
  		spin_lock_irq(q->queue_lock);
  		if (val)
  			queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  		else
  			queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
  		spin_unlock_irq(q->queue_lock);
  	}
  
  	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;
  
  	ret = q->rq_timed_out_fn(req);
  	switch (ret) {
  	case BLK_EH_HANDLED:
  		__blk_complete_request(req);
  		break;
  	case BLK_EH_RESET_TIMER:
  		blk_clear_rq_complete(req);
  		blk_add_timer(req);
  		break;
  	case BLK_EH_NOT_HANDLED:
  		/*
  		 * 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\n", ret);
  		break;
  	}
  }
  
  void blk_rq_timed_out_timer(unsigned long data)
  {
  	struct request_queue *q = (struct request_queue *) data;
  	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) {
  		if (time_after_eq(jiffies, rq->deadline)) {
  			list_del_init(&rq->timeout_list);
  
  			/*
  			 * Check if we raced with end io completion
  			 */
  			if (blk_mark_rq_complete(rq))
  				continue;
  			blk_rq_timed_out(rq);
  		} else if (!next_set || time_after(next, rq->deadline)) {
  			next = rq->deadline;
  			next_set = 1;
  		}
  	}
  
  	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 (blk_mark_rq_complete(req))
  		return;
  	blk_delete_timer(req);
  	blk_rq_timed_out(req);
  }
  EXPORT_SYMBOL_GPL(blk_abort_request);
  
  /**
   * 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->rq_timed_out_fn)
  		return;
  
  	BUG_ON(!list_empty(&req->timeout_list));
  	BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
  
  	/*
  	 * 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->deadline = jiffies + req->timeout;
  	list_add_tail(&req->timeout_list, &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 = round_jiffies_up(req->deadline);
  
  	if (!timer_pending(&q->timeout) ||
  	    time_before(expiry, q->timeout.expires))
  		mod_timer(&q->timeout, expiry);
  }
  
  /**
   * blk_abort_queue -- Abort all request on given queue
   * @queue:	pointer to queue
   *
   */
  void blk_abort_queue(struct request_queue *q)
  {
  	unsigned long flags;
  	struct request *rq, *tmp;
  	LIST_HEAD(list);
  
  	/*
  	 * Not a request based block device, nothing to abort
  	 */
  	if (!q->request_fn)
  		return;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  
  	elv_abort_queue(q);
  
  	/*
  	 * Splice entries to local list, to avoid deadlocking if entries
  	 * get readded to the timeout list by error handling
  	 */
  	list_splice_init(&q->timeout_list, &list);
  
  	list_for_each_entry_safe(rq, tmp, &list, timeout_list)
  		blk_abort_request(rq);
  
  	/*
  	 * Occasionally, blk_abort_request() will return without
  	 * deleting the element from the list. Make sure we add those back
  	 * instead of leaving them on the local stack list.
  	 */
  	list_splice(&list, &q->timeout_list);
  
  	spin_unlock_irqrestore(q->queue_lock, flags);
  
  }
  EXPORT_SYMBOL_GPL(blk_abort_queue);
  