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 */
  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);
 122
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