[SCSI] fix sym scsi boot hang

On Wed, 2005-09-14 at 18:06 +1000, Anton Blanchard wrote:
> And in particular it looks like the scsi_unprep_request in
> scsi_queue_insert is causing it. The following patch fixes the boot
> problems on the vscsi machine:

OK, my fault.  Your fix is almost correct .. I was going to do this
eventually, honest, because there's no need to unprep and reprep a
command that comes in through scsi_queue_insert().

However, I decided to leave it in to exercise the scsi_unprep_request()
path just to make sure it was working.  What's happening, I think, is
that we also use this path for retries.  Since we kill and reget the
command each time, the retries decrement is never seen, so we're
retrying forever.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_lib.c

@@ -140,14 +140,12 @@ static void scsi_unprep_request(struct request *req)
  *              commands.
  * Notes:       This could be called either from an interrupt context or a
  *              normal process context.
- * Notes:	Upon return, cmd is a stale pointer.
  */
 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 {
 	struct Scsi_Host *host = cmd->device->host;
 	struct scsi_device *device = cmd->device;
 	struct request_queue *q = device->request_queue;
-	struct request *req = cmd->request;
 	unsigned long flags;
 
 	SCSI_LOG_MLQUEUE(1,
@@ -188,9 +186,8 @@ int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 	 * function.  The SCSI request function detects the blocked condition
 	 * and plugs the queue appropriately.
          */
-	scsi_unprep_request(req);
 	spin_lock_irqsave(q->queue_lock, flags);
-	blk_requeue_request(q, req);
+	blk_requeue_request(q, cmd->request);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 
 	scsi_run_queue(q);