IRP_MJ_FILE_SYSTEM_CONTROL (FS and filter drivers)
When Sent
The I/O Manager, other operating system components, and other kernel-mode drivers send IRP_MJ_FILE_SYSTEM_CONTROL requests. It can be sent, for example, when a user-mode application has called the Win32 DeviceIoControl function to send a file system I/O control (FSCTL) request.
Operation: File System Drivers
The file system driver or recognizer should check the minor function code to determine which file system control operation is requested.
File system drivers should handle the following minor function codes:
| Code | Description |
|---|---|
| IRP_MN_KERNEL_CALL | This request is the same as IRP_MN_USER_FS_REQUEST (described following), except that the source of the request is a trusted kernel component. |
| IRP_MN_MOUNT_VOLUME | Indicates a volume mount request. If a file system driver receives this IRP for a volume whose format doesn't match that of the file system, the file system driver should return STATUS_UNRECOGNIZED_VOLUME. |
| IRP_MN_USER_FS_REQUEST | Indicates an FSCTL request, possibly on behalf of a user-mode application that has called the Microsoft Win32 DeviceIoControl function or on behalf of a kernel-mode component that has called ZwDeviceIoControlFile or IoBuildDeviceIoControlRequest. For detailed information about FSCTL requests, see "Device Input and Output Control Codes" in the Windows SDK documentation. |
| IRP_MN_VERIFY_VOLUME | Indicates a volume verification request. For removable media, the file system must verify the volume when it detects that the media has been removed and returned to ensure that it's still the same known volume. If the volume has changed, the file system should invalidate all outstanding handles. It should also return an error if the file system on this new media has changed. This request is most often used for floppy drives. |
File system recognizers must handle the following minor function code:
| Code | Description |
|---|---|
| IRP_MN_LOAD_FILE_SYSTEM | Indicates a load-file system request. |
The file system driver or recognizer should perform the requested operation and then complete the IRP.
Operation: Legacy Files System Filter Drivers
The filter driver should pass this IRP down to the next-lower driver on the stack.
Parameters
A file system or filter driver calls IoGetCurrentIrpStackLocation for the given IRP to get a pointer to its own stack location in the IRP. In the following parameters, Irp points to the IRP and IrpSp points to the IO_STACK_LOCATION. The driver can use the information set in the following members of the IRP and IRP stack location to process a file system control request:
DeviceObject is a pointer to the target device object.
Irp->AssociatedIrp.SystemBuffer points to a system-supplied input buffer to be passed to the file system or file system filter driver for the target volume. Used for METHOD_BUFFERED or METHOD_DIRECT I/O. Whether this parameter is required depends on the specific file system control code.
Irp->IoStatus points to an IO_STATUS_BLOCK structure that receives the final completion status and information about the requested operation.
Irp->MdlAddress is the address of a memory descriptor list (MDL) describing an output buffer to be passed to the file system or file system filter driver for the target volume. Used for METHOD_DIRECT I/O. Whether this parameter is required depends on the specific I/O control code.
Irp->UserBuffer points to a caller-supplied output buffer to be passed to the file system or file system filter driver for the target volume. Used for METHOD_BUFFERED or METHOD_NEITHER I/O. Whether this parameter is optional or required depends on the specific I/O control code.
IrpSp->FileObject points to the file object that is associated with DeviceObject.
The IrpSp->FileObject parameter contains a pointer to the RelatedFileObject field, which is also a FILE_OBJECT structure. The RelatedFileObject field of the FILE_OBJECT structure isn't valid during the processing of IRP_MJ_FILE_SYSTEM_CONTROL and shouldn't be used.
IrpSp->Flags can be set to SL_ALLOW_RAW_MOUNT for IRP_MN_VERIFY_VOLUME.
IrpSp->MajorFunction is set to IRP_MJ_FILE_SYSTEM_CONTROL.
IrpSp->MinorFunction can be set to one of the following values.
- IRP_MN_KERNEL_CALL
- IRP_MN_LOAD_FILE_SYSTEM
- IRP_MN_MOUNT_VOLUME
- IRP_MN_USER_FS_REQUEST
- IRP_MN_VERIFY_VOLUME
IrpSp->Parameters.FileSystemControl.FsControlCode is the FSCTL function code to be passed to the file system or file system filter driver for the target volume. For use with IRP_MN_USER_FS_REQUEST only.
For detailed information about IOCTL and FSCTL requests, see Using I/O Control Codes and "Device Input and Output Control Codes" in the Windows SDK documentation.
IrpSp->Parameters.FileSystemControl.InputBufferLength is the size in bytes of the buffer pointed to by Irp->AssociatedIrp.SystemBuffer.
IrpSp->Parameters.FileSystemControl.OutputBufferLength is the size in bytes of the buffer pointed to by Irp->UserBuffer.
IrpSp->Parameters.FileSystemControl.Type3InputBuffer is the input buffer for kernel-mode requests using METHOD_NEITHER.
IrpSp->Parameters.MountVolume.DeviceObject points to the device object for the actual device on which the volume is to be mounted. File system filter drivers shouldn't use this parameter.
IrpSp->Parameters.MountVolume.Vpb points to the volume parameter block (VPB) for the volume to be mounted. File systems that support removable media might substitute a previously used VPB for the one passed in this parameter. On such file systems, after the volume is mounted, this pointer can no longer be assumed to be valid. File system filter drivers that filter these file systems should use this parameter as follows: The filter should save the value of IrpSp->Parameters.MountVolume.Vpb->RealDevice before it sends the IRP down to lower-level drivers. After the volume is successfully mounted, the filter can use this pointer to the storage device object to obtain the correct VPB pointer.
IrpSp->Parameters.VerifyVolume.DeviceObject points to the device object for the volume to be verified.
IrpSp->Parameters.VerifyVolume.Vpb points to the VPB for the volume to be verified.