[S390] dasd: fix race condition in resume code

There is a race while re-reading the device characteristics. After
cleaning the memory area a cqr is build which reads the device
characteristics. This may take a rather long time and the device
characteristics structure is zero during this. Now it could be
possible that the block tasklet starts working and a new cqr will be
build. The build_cp command refers to the device characteristics
structure and this may lead into a divide by zero exception.
Fix this by re-reading the device characteristics into a temporary
structur and copy the data to the original structure. Also take the
ccwdev_lock.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd.c

@@ -2508,8 +2508,6 @@ int dasd_generic_restore_device(struct ccw_device *cdev)
 	device->stopped &= ~DASD_UNRESUMED_PM;
 
 	dasd_schedule_device_bh(device);
-	if (device->block)
-		dasd_schedule_block_bh(device->block);
 
 	if (device->discipline->restore)
 		rc = device->discipline->restore(device);
@@ -2520,6 +2518,9 @@ int dasd_generic_restore_device(struct ccw_device *cdev)
 		 */
 		device->stopped |= DASD_UNRESUMED_PM;
 
+	if (device->block)
+		dasd_schedule_block_bh(device->block);
+
 	dasd_put_device(device);
 	return 0;
 }

drivers/s390/block/dasd_eckd.c

@@ -2338,6 +2338,8 @@ static struct dasd_ccw_req *dasd_eckd_build_cp(struct dasd_device *startdev,
 	/* Calculate number of blocks/records per track. */
 	blksize = block->bp_block;
 	blk_per_trk = recs_per_track(&private->rdc_data, 0, blksize);
+	if (blk_per_trk == 0)
+		return ERR_PTR(-EINVAL);
 	/* Calculate record id of first and last block. */
 	first_rec = first_trk = blk_rq_pos(req) >> block->s2b_shift;
 	first_offs = sector_div(first_trk, blk_per_trk);
@@ -3211,6 +3213,7 @@ int dasd_eckd_pm_freeze(struct dasd_device *device)
 int dasd_eckd_restore_device(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private;
+	struct dasd_eckd_characteristics temp_rdc_data;
 	int is_known, rc;
 	struct dasd_uid temp_uid;
 
@@ -3245,15 +3248,17 @@ int dasd_eckd_restore_device(struct dasd_device *device)
 	dasd_eckd_read_features(device);
 
 	/* Read Device Characteristics */
-	memset(&private->rdc_data, 0, sizeof(private->rdc_data));
 	rc = dasd_generic_read_dev_chars(device, DASD_ECKD_MAGIC,
-					 &private->rdc_data, 64);
+					 &temp_rdc_data, 64);
 	if (rc) {
 		DBF_EVENT(DBF_WARNING,
 			  "Read device characteristics failed, rc=%d for "
 			  "device: %s", rc, dev_name(&device->cdev->dev));
 		goto out_err;
 	}
+	spin_lock(get_ccwdev_lock(device->cdev));
+	memcpy(&private->rdc_data, &temp_rdc_data, sizeof(temp_rdc_data));
+	spin_unlock(get_ccwdev_lock(device->cdev));
 
 	/* add device to alias management */
 	dasd_alias_add_device(device);