ide: dequeue in-flight request

ide generally has single request in flight and tracks it using
hwif->rq and all state handlers follow the following convention.

* ide_started is returned if the request is in flight.

* ide_stopped is returned if the queue needs to be restarted.  The
  request might or might not have been processed fully or partially.

* hwif->rq is set to NULL, when an issued request completes.

So, dequeueing model can be implemented by dequeueing after fetch,
requeueing if hwif->rq isn't NULL on ide_stopped return and doing
about the same thing on completion / port unlock paths.  These changes
can be made in ide-io proper.

In addition to the above main changes, the following updates are
necessary.

* ide-cd shouldn't dequeue a request when issuing REQUEST SENSE for it
  as the request is already dequeued.

* ide-atapi uses request queue as stack when issuing REQUEST SENSE to
  put the REQUEST SENSE in front of the failed request.  This now
  needs to be done using requeueing.

[ Impact: dequeue in-flight request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 792534db8f85..2874c3d703a9 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -246,6 +246,7 @@ EXPORT_SYMBOL_GPL(ide_queue_sense_rq);
  */
 void ide_retry_pc(ide_drive_t *drive)
 {
+        struct request *failed_rq = drive->hwif->rq;
         struct request *sense_rq = &drive->sense_rq;
         struct ide_atapi_pc *pc = &drive->request_sense_pc;
 
@@ -260,8 +261,17 @@ void ide_retry_pc(ide_drive_t *drive)
         if (drive->media == ide_tape)
                 set_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags);
 
-        if (ide_queue_sense_rq(drive, pc))
-                ide_complete_rq(drive, -EIO, blk_rq_bytes(drive->hwif->rq));
+        /*
+         * Push back the failed request and put request sense on top
+         * of it.  The failed command will be retried after sense data
+         * is acquired.
+         */
+        blk_requeue_request(failed_rq->q, failed_rq);
+        drive->hwif->rq = NULL;
+        if (ide_queue_sense_rq(drive, pc)) {
+                blkdev_dequeue_request(failed_rq);
+                ide_complete_rq(drive, -EIO, blk_rq_bytes(failed_rq));
+        }
 }
 EXPORT_SYMBOL_GPL(ide_retry_pc);