1/*
  2 * Functions related to setting various queue properties from drivers
  3 */
  4#include <linux/kernel.h>
  5#include <linux/module.h>
  6#include <linux/bio.h>
  7#include <linux/blkdev.h>
  8
  9#include "blk.h"
 10
 11/*
 12 * for max sense size
 13 */
 14#include <scsi/scsi_cmnd.h>
 15
 16/**
 17 * blk_end_sync_rq - executes a completion event on a request
 18 * @rq: request to complete
 19 * @error: end I/O status of the request
 20 */
 21static void blk_end_sync_rq(struct request *rq, int error)
 22{
 23	struct completion *waiting = rq->end_io_data;
 24
 25	rq->end_io_data = NULL;
 26	__blk_put_request(rq->q, rq);
 27
 28	/*
 29	 * complete last, if this is a stack request the process (and thus
 30	 * the rq pointer) could be invalid right after this complete()
 31	 */
 32	complete(waiting);
 33}
 34
 35/**
 36 * blk_execute_rq_nowait - insert a request into queue for execution
 37 * @q:		queue to insert the request in
 38 * @bd_disk:	matching gendisk
 39 * @rq:		request to insert
 40 * @at_head:    insert request at head or tail of queue
 41 * @done:	I/O completion handler
 42 *
 43 * Description:
 44 *    Insert a fully prepared request at the back of the I/O scheduler queue
 45 *    for execution.  Don't wait for completion.
 46 */
 47void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 48			   struct request *rq, int at_head,
 49			   rq_end_io_fn *done)
 50{
 51	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
 52
 53	WARN_ON(irqs_disabled());
 54	spin_lock_irq(q->queue_lock);
 55
 56	if (unlikely(blk_queue_dead(q))) {
 57		spin_unlock_irq(q->queue_lock);
 58		rq->errors = -ENXIO;
 59		if (rq->end_io)
 60			rq->end_io(rq, rq->errors);
 61		return;
 62	}
 63
 64	rq->rq_disk = bd_disk;
 65	rq->end_io = done;
 66	__elv_add_request(q, rq, where);
 67	__blk_run_queue(q);
 68	/* the queue is stopped so it won't be run */
 69	if (rq->cmd_type == REQ_TYPE_PM_RESUME)
 70		q->request_fn(q);
 71	spin_unlock_irq(q->queue_lock);
 72}
 73EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
 74
 75/**
 76 * blk_execute_rq - insert a request into queue for execution
 77 * @q:		queue to insert the request in
 78 * @bd_disk:	matching gendisk
 79 * @rq:		request to insert
 80 * @at_head:    insert request at head or tail of queue
 81 *
 82 * Description:
 83 *    Insert a fully prepared request at the back of the I/O scheduler queue
 84 *    for execution and wait for completion.
 85 */
 86int blk_execute_rq(struct request_queue *q, struct gendisk *bd_disk,
 87		   struct request *rq, int at_head)
 88{
 89	DECLARE_COMPLETION_ONSTACK(wait);
 90	char sense[SCSI_SENSE_BUFFERSIZE];
 91	int err = 0;
 92	unsigned long hang_check;
 93
 94	/*
 95	 * we need an extra reference to the request, so we can look at
 96	 * it after io completion
 97	 */
 98	rq->ref_count++;
 99
100	if (!rq->sense) {
101		memset(sense, 0, sizeof(sense));
102		rq->sense = sense;
103		rq->sense_len = 0;
104	}
105
106	rq->end_io_data = &wait;
107	blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
108
109	/* Prevent hang_check timer from firing at us during very long I/O */
110	hang_check = sysctl_hung_task_timeout_secs;
111	if (hang_check)
112		while (!wait_for_completion_timeout(&wait, hang_check * (HZ/2)));
113	else
114		wait_for_completion(&wait);
115
116	if (rq->errors)
117		err = -EIO;
118
119	return err;
120}
121EXPORT_SYMBOL(blk_execute_rq);