ide: Requeue request after DMA timeout

I noticed that my KVM virtual machines were experiencing IDE
issues resulting in processes stuck on waiting for buffers to
complete.

The root cause is of course race conditions in the ancient qemu
backend that I'm using.  However, the fact that the guest isn't
recovering is a bug.

I've tracked it down to the change made last year to dequeue
requests at the start rather than at the end in the IDE layer.

commit 8f6205cd57
Author: Tejun Heo <tj@kernel.org>
Date:   Fri May 8 11:53:59 2009 +0900

    ide: dequeue in-flight request

The problem is that the function ide_dma_timeout_retry does not
requeue the current request, causing one request to be lost for
each DMA timeout.

This patch fixes this by requeueing the request.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ide/ide-dma.c

@@ -492,6 +492,7 @@ ide_startstop_t ide_dma_timeout_retry(ide_drive_t *drive, int error)
 	if (rq) {
 		hwif->rq = NULL;
 		rq->errors = 0;
+		ide_requeue_and_plug(drive, rq);
 	}
 	return ret;
 }