[PATCH] s390: dasd failfast support

To properly support multipath-failover handling, the linux block layer has
introduced a special request flag, 'REQ_FAILFAST'.  This flag is now used to
return requests immediately in case the device is not operational.

Signed-off-by: Horst Hummel <horst.hummel@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 20 insertions, 8 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 62787393a209..1141a5963b67 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -7,7 +7,7 @@
  * Bugreports.to..: <Linux390@de.ibm.com>
  * (C) IBM Corporation, IBM Deutschland Entwicklung GmbH, 1999-2001
  *
- * $Revision: 1.169 $
+ * $Revision: 1.172 $
  */
 
 #include <linux/config.h>
@@ -1224,6 +1224,12 @@ __dasd_start_head(struct dasd_device * device)
 	if (list_empty(&device->ccw_queue))
 		return;
 	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, list);
+        /* check FAILFAST */
+	if (device->stopped & ~DASD_STOPPED_PENDING &&
+	    test_bit(DASD_CQR_FLAGS_FAILFAST, &cqr->flags)) {
+		cqr->status = DASD_CQR_FAILED;
+		dasd_schedule_bh(device);
+	}
 	if ((cqr->status == DASD_CQR_QUEUED) &&
 	    (!device->stopped)) {
 		/* try to start the first I/O that can be started */
@@ -1750,8 +1756,10 @@ dasd_exit(void)
  * SECTION: common functions for ccw_driver use
  */
 
-/* initial attempt at a probe function. this can be simplified once
- * the other detection code is gone */
+/*
+ * Initial attempt at a probe function. this can be simplified once
+ * the other detection code is gone.
+ */
 int
 dasd_generic_probe (struct ccw_device *cdev,
 		    struct dasd_discipline *discipline)
@@ -1770,8 +1778,10 @@ dasd_generic_probe (struct ccw_device *cdev,
 	return ret;
 }
 
-/* this will one day be called from a global not_oper handler.
- * It is also used by driver_unregister during module unload */
+/*
+ * This will one day be called from a global not_oper handler.
+ * It is also used by driver_unregister during module unload.
+ */
 void
 dasd_generic_remove (struct ccw_device *cdev)
 {
@@ -1798,9 +1808,11 @@ dasd_generic_remove (struct ccw_device *cdev)
 	dasd_delete_device(device);
 }
 
-/* activate a device. This is called from dasd_{eckd,fba}_probe() when either
+/*
+ * Activate a device. This is called from dasd_{eckd,fba}_probe() when either
  * the device is detected for the first time and is supposed to be used
- * or the user has started activation through sysfs */
+ * or the user has started activation through sysfs.
+ */
 int
 dasd_generic_set_online (struct ccw_device *cdev,
 			 struct dasd_discipline *discipline)
@@ -1917,7 +1929,6 @@ dasd_generic_notify(struct ccw_device *cdev, int event)
 				if (cqr->status == DASD_CQR_IN_IO)
 					cqr->status = DASD_CQR_FAILED;
 			device->stopped |= DASD_STOPPED_DC_EIO;
-			dasd_schedule_bh(device);
 		} else {
 			list_for_each_entry(cqr, &device->ccw_queue, list)
 				if (cqr->status == DASD_CQR_IN_IO) {
@@ -1927,6 +1938,7 @@ dasd_generic_notify(struct ccw_device *cdev, int event)
 			device->stopped |= DASD_STOPPED_DC_WAIT;
 			dasd_set_timer(device, 0);
 		}
+		dasd_schedule_bh(device);
 		ret = 1;
 		break;
 	case CIO_OPER: