s390/dasd: fix failing path verification

DASD path verification requires the usage of sleep_on_immediatly to
ensure that no other I/O request is blocking the recovery of
disconnected devices. But two concurrent path verification workers for
the same device may kill each others requests due to the usage of the
immediate sleep_on function. This may lead to unsuccessful path
verifications.

Prevent that two parallel path verification workers conflict with
each other by implementing a device flag signalling a already running
worker.
Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_eckd.c

@@ -1259,7 +1259,11 @@ static void do_path_verification_work(struct work_struct *work)
 		schedule_work(work);
 		return;
 	}
-
+	/* check if path verification already running and delay if so */
+	if (test_and_set_bit(DASD_FLAG_PATH_VERIFY, &device->flags)) {
+		schedule_work(work);
+		return;
+	}
 	opm = 0;
 	npm = 0;
 	ppm = 0;
@@ -1402,7 +1406,7 @@ static void do_path_verification_work(struct work_struct *work)
 		device->path_data.hpfpm |= hpfpm;
 		spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 	}
-
+	clear_bit(DASD_FLAG_PATH_VERIFY, &device->flags);
 	dasd_put_device(device);
 	if (data->isglobal)
 		mutex_unlock(&dasd_path_verification_mutex);

drivers/s390/block/dasd_int.h

@@ -534,6 +534,7 @@ struct dasd_attention_data {
 #define DASD_FLAG_SAFE_OFFLINE	10	/* safe offline processing requested*/
 #define DASD_FLAG_SAFE_OFFLINE_RUNNING	11	/* safe offline running */
 #define DASD_FLAG_ABORTALL	12	/* Abort all noretry requests */
+#define DASD_FLAG_PATH_VERIFY	13	/* Path verification worker running */
 
 #define DASD_SLEEPON_START_TAG	((void *) 1)
 #define DASD_SLEEPON_END_TAG	((void *) 2)