s390/dasd: fix possibly missed path verification

__dasd_device_check_path_events() calls the discipline path event handler.
This handler can leave the 'to be verified pathmask' populated for an
additional verification.

There is a race window where the worker has finished before
dasd_path_clear_all_verify() is called which resets the tbvpm.

Due to this there could be outstanding path verifications missed.

Fix by clearing the pathmasks before calling the handler and add them
again in case of an error.
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20211020115124.1735254-8-sth@linux.ibm.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/s390/block/dasd.c

@@ -2077,12 +2077,15 @@ static void __dasd_device_check_path_events(struct dasd_device *device)
 
 	if (device->stopped & ~(DASD_STOPPED_DC_WAIT))
 		return;
+
+	dasd_path_clear_all_verify(device);
+	dasd_path_clear_all_fcsec(device);
+
 	rc = device->discipline->pe_handler(device, tbvpm, fcsecpm);
 	if (rc) {
+		dasd_path_add_tbvpm(device, tbvpm);
+		dasd_path_add_fcsecpm(device, fcsecpm);
 		dasd_device_set_timer(device, 50);
-	} else {
-		dasd_path_clear_all_verify(device);
-		dasd_path_clear_all_fcsec(device);
 	}
 };
 

drivers/s390/block/dasd_int.h

@@ -1305,6 +1305,15 @@ static inline void dasd_path_add_ppm(struct dasd_device *device, __u8 pm)
 			dasd_path_preferred(device, chp);
 }
 
+static inline void dasd_path_add_fcsecpm(struct dasd_device *device, __u8 pm)
+{
+	int chp;
+
+	for (chp = 0; chp < 8; chp++)
+		if (pm & (0x80 >> chp))
+			dasd_path_fcsec(device, chp);
+}
+
 /*
  * set functions for path masks
  * the existing path mask will be replaced by the given path mask