linux/block/blk-exec.c
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   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 *
  47 * Note:
  48 *    This function will invoke @done directly if the queue is dead.
  49 */
  50void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
  51                           struct request *rq, int at_head,
  52                           rq_end_io_fn *done)
  53{
  54        int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
  55
  56        WARN_ON(irqs_disabled());
  57
  58        rq->rq_disk = bd_disk;
  59        rq->end_io = done;
  60
  61        spin_lock_irq(q->queue_lock);
  62
  63        if (unlikely(blk_queue_dead(q))) {
  64                rq->errors = -ENXIO;
  65                if (rq->end_io)
  66                        rq->end_io(rq, rq->errors);
  67                spin_unlock_irq(q->queue_lock);
  68                return;
  69        }
  70
  71        __elv_add_request(q, rq, where);
  72        __blk_run_queue(q);
  73        /* the queue is stopped so it won't be run */
  74        if (rq->cmd_type == REQ_TYPE_PM_RESUME)
  75                q->request_fn(q);
  76        spin_unlock_irq(q->queue_lock);
  77}
  78EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
  79
  80/**
  81 * blk_execute_rq - insert a request into queue for execution
  82 * @q:          queue to insert the request in
  83 * @bd_disk:    matching gendisk
  84 * @rq:         request to insert
  85 * @at_head:    insert request at head or tail of queue
  86 *
  87 * Description:
  88 *    Insert a fully prepared request at the back of the I/O scheduler queue
  89 *    for execution and wait for completion.
  90 */
  91int blk_execute_rq(struct request_queue *q, struct gendisk *bd_disk,
  92                   struct request *rq, int at_head)
  93{
  94        DECLARE_COMPLETION_ONSTACK(wait);
  95        char sense[SCSI_SENSE_BUFFERSIZE];
  96        int err = 0;
  97        unsigned long hang_check;
  98
  99        /*
 100         * we need an extra reference to the request, so we can look at
 101         * it after io completion
 102         */
 103        rq->ref_count++;
 104
 105        if (!rq->sense) {
 106                memset(sense, 0, sizeof(sense));
 107                rq->sense = sense;
 108                rq->sense_len = 0;
 109        }
 110
 111        rq->end_io_data = &wait;
 112        blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
 113
 114        /* Prevent hang_check timer from firing at us during very long I/O */
 115        hang_check = sysctl_hung_task_timeout_secs;
 116        if (hang_check)
 117                while (!wait_for_completion_timeout(&wait, hang_check * (HZ/2)));
 118        else
 119                wait_for_completion(&wait);
 120
 121        if (rq->errors)
 122                err = -EIO;
 123
 124        return err;
 125}
 126EXPORT_SYMBOL(blk_execute_rq);
 127
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