block: unify request timeout handling

Right now SCSI and others do their own command timeout handling.
Move those bits to the block layer.

Instead of having a timer per command, we try to be a bit more clever
and simply have one per-queue. This avoids the overhead of having to
tear down and setup a timer for each command, so it will result in a lot
less timer fiddling.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/scsi/scsi_transport.h

@@ -21,6 +21,7 @@
 #define SCSI_TRANSPORT_H
 
 #include <linux/transport_class.h>
+#include <linux/blkdev.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_device.h>
 
@@ -64,7 +65,7 @@ struct scsi_transport_template {
 	 *			begin counting again
 	 * EH_NOT_HANDLED	Begin normal error recovery
 	 */
-	enum scsi_eh_timer_return (* eh_timed_out)(struct scsi_cmnd *);
+	enum blk_eh_timer_return (*eh_timed_out)(struct scsi_cmnd *);
 
 	/*
 	 * Used as callback for the completion of i_t_nexus request