IoWritePartitionTableEx function (ntddk.h)

The IoWritePartitionTableEx routine writes partition tables from the entries in the partition list buffer for each partition on the disk represented by the given device object.


NTSTATUS IoWritePartitionTableEx(
  PDEVICE_OBJECT               DeviceObject,



[in] Pointer to the device object representing the disk whose partition tables are to be written.


Pointer to the drive layout buffer that contains the partition list entries. For more detailed information see DRIVE_LAYOUT_INFORMATION_EX.

Return value

IoWritePartitionTabloEx returns a status code of STATUS_SUCCESS if all writes were completed without error. In case of failure, the error codes returned by IoWritePartitionTableEx might include, but are not limited to, the following list:

Return code Description
Indicates a failure read the correct disk geometry.
Indicates a failure to allocate necessary resources (for example, heap memory, IRPs, and so on).
Indicates that sector zero did not have the expected MBR disk signature.


IoWritePartitionTableEx replaces the obsolete routine IoWritePartitionTable. Unlike the older routine, it can write to GUID Partition Tables as well as Master Boot Record Partition Tables.

IoWritePartitionTableEx must only be used by disk drivers. Other drivers should use the IOCTL_DISK_SET_DRIVE_LAYOUT_EX disk I/O request instead.

When a disk device driver receives an IRP_MJ_DEVICE_CONTROL request to set the partition type in a partition table entry, or to repartition the disk, it should call IoWritePartionTableEx. The device control request is generally issued by the format utility, which performs I/O control functions on the partitions and disks in the machine.

To reset a partition type, the driver passes a pointer to the device object, representing the physical disk, and the number of the partition associated with the device object that the format utility has open. When a disk is to be repartitioned dynamically, the disk driver must tear down its set of device objects representing the current disk partitions and create a new set of device objects representing the new partitions on the disk.

In order tot create or delete partitions a full description of the system must be obtained by a call to IoReadPartitionTableEx. The drive layout structure can be modified by the system format utility to reflect a new configuration of the disk.

IoWritePartitionTableEx is synchronous. It must be called by the disk driver's Dispatch routine or by a driver thread. Thus, all user and file system threads must be prepared to enter a wait state when issuing the device control request to reset partition types for the device.


Target Platform Universal
Header ntddk.h (include Ntddk.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
DDI compliance rules HwStorPortProhibitedDDIs

See also