block: convert to dequeueing model (easy ones)

plat-omap/mailbox, floppy, viocd, mspro_block, i2o_block and
mmc/card/queue are already pretty close to dequeueing model and can be
converted with simple changes.  Convert them.

While at it,

* xen-blkfront: !fs check moved downwards to share dequeue call with
  normal path.

* mspro_block: __blk_end_request(..., blk_rq_cur_byte()) converted to
  __blk_end_request_cur()

* mmc/card/queue: loop of __blk_end_request() converted to
  __blk_end_request_all()

[ Impact: dequeue in-flight request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/arch/arm/plat-omap/mailbox.c b/arch/arm/plat-omap/mailbox.c
index 538ba75..7a1f5c2 100644
--- a/arch/arm/plat-omap/mailbox.c
+++ b/arch/arm/plat-omap/mailbox.c
@@ -198,6 +198,8 @@
 
 		spin_lock(q->queue_lock);
 		rq = elv_next_request(q);
+		if (rq)
+			blkdev_dequeue_request(rq);
 		spin_unlock(q->queue_lock);
 
 		if (!rq)
@@ -208,6 +210,9 @@
 		ret = __mbox_msg_send(mbox, tx_data->msg, tx_data->arg);
 		if (ret) {
 			enable_mbox_irq(mbox, IRQ_TX);
+			spin_lock(q->queue_lock);
+			blk_requeue_request(q, rq);
+			spin_unlock(q->queue_lock);
 			return;
 		}
 
@@ -238,6 +243,8 @@
 	while (1) {
 		spin_lock_irqsave(q->queue_lock, flags);
 		rq = elv_next_request(q);
+		if (rq)
+			blkdev_dequeue_request(rq);
 		spin_unlock_irqrestore(q->queue_lock, flags);
 		if (!rq)
 			break;
@@ -345,6 +352,8 @@
 	while (1) {
 		spin_lock_irqsave(q->queue_lock, flags);
 		rq = elv_next_request(q);
+		if (rq)
+			blkdev_dequeue_request(rq);
 		spin_unlock_irqrestore(q->queue_lock, flags);
 
 		if (!rq)