block/blk-exec.c

   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  */
  21 static 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 void 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 }
  73 EXPORT_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  */
  86 int 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 }
 121 EXPORT_SYMBOL(blk_execute_rq);