kernel/disk_device_manager: Continue scanning after invalid partitions.

As the inline comment notes, just because we could not scan one
partition does not mean we won't be able to scan the following ones.
This fixes scanning for disks on certain systems following axeld's
change in 7c2135591b.

Part of #15330.

src/system/kernel/disk_device_manager/KDiskDeviceManager.cpp

@@ -986,31 +986,33 @@ KDiskDeviceManager::LoadNextDiskSystem(int32* cookie)
 status_t
 KDiskDeviceManager::InitialDeviceScan()
 {
-	status_t error = B_ERROR;
-
 	// scan for devices
 	if (ManagerLocker locker = this) {
-		error = _Scan("/dev/disk");
+		status_t error = _Scan("/dev/disk");
 		if (error != B_OK)
 			return error;
 	}
 
 	// scan the devices for partitions
 	int32 cookie = 0;
+	status_t status = B_OK;
 	while (KDiskDevice* device = RegisterNextDevice(&cookie)) {
 		PartitionRegistrar _(device, true);
 		if (DeviceWriteLocker deviceLocker = device) {
 			if (ManagerLocker locker = this) {
-				error = _ScanPartition(device, false);
+				status_t error = _ScanPartition(device, false);
 				device->UnmarkBusy(true);
 				if (error != B_OK)
-					break;
+					status = error;
+				// Even if we could not scan this partition, we want to try
+				// and scan the rest. Just because one partition is invalid
+				// or unscannable does not mean the ones after it are.
 			} else
 				return B_ERROR;
 		} else
 			return B_ERROR;
 	}
-	return error;
+	return status;
 }
 
 
@@ -1091,21 +1093,23 @@ KDiskDeviceManager::RescanDiskSystems()
 
 	// rescan existing devices with the new disk systems
 	int32 cookie = 0;
+	status_t status = B_OK;
 	while (KDiskDevice* device = RegisterNextDevice(&cookie)) {
 		PartitionRegistrar _(device, true);
 		if (DeviceWriteLocker deviceLocker = device) {
 			if (ManagerLocker locker = this) {
-				status_t status = _ScanPartition(device, false, &addedSystems);
+				status_t error = _ScanPartition(device, false, &addedSystems);
 				device->UnmarkBusy(true);
-				if (status != B_OK)
-					break;
+				if (error != B_OK)
+					status = error;
+				// See comment in InitialDeviceScan().
 			} else
 				return B_ERROR;
 		} else
 			return B_ERROR;
 	}
 
-	return B_OK;
+	return status;
 }