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FLT_PARAMETERS for IRP_MJ_WRITE union

  • Article

The following union component is used when the MajorFunction field of the FLT_IO_PARAMETER_BLOCK structure for the operation is IRP_MJ_WRITE.

Syntax

typedef union _FLT_PARAMETERS {
  ...    ;
  struct {
    ULONG         Length;
    ULONG         Key;
    LARGE_INTEGER ByteOffset;
    PVOID         WriteBuffer;
    PMDL          MdlAddress;
  } Write;
  ...    ;
} FLT_PARAMETERS, *PFLT_PARAMETERS;

Members

  • Write: Structure containing the following members.

  • Length: Length, in bytes, of the data to be written.

  • Key: Key value associated with a byte-range lock on the target file.

  • ByteOffset: Starting byte offset within the file of the data to be written.

  • WriteBuffer: Pointer to a buffer that contains the data to be written to the file. This member is optional and can be NULL if a MDL is provided in MdlAddress. See Remarks.

  • MdlAddress: Address of a memory descriptor list (MDL) that describes the buffer that the WriteBuffer member points to. This member is optional and can be NULL if a buffer is provided in WriteBuffer. See Remarks.

Remarks

The FLT_PARAMETERS structure for IRP_MJ_WRITE operations contains the parameters for a write operation represented by a callback data (FLT_CALLBACK_DATA) structure. It is contained in an FLT_IO_PARAMETER_BLOCK structure.

If both a WriteBuffer and MdlAddress buffer are provided, it is recommended that minifilters use the MDL. The memory that WriteBuffer points to is valid when it is a user mode address being accessed within the context of the calling process, or if it is a kernel mode address.

If a minifilter changes the value of MdlAddress, then after its post operation callback, Filter Manager will free the MDL currently stored in MdlAddress and restore the previous value of MdlAddress.

IRP_MJ_WRITE can be an IRP-based operation or a fast I/O operation.

Requirements

Requirement type Requirement
Header Fltkernel.h (include Fltkernel.h)

See also

FLT_CALLBACK_DATA

FLT_IO_PARAMETER_BLOCK

FLT_IS_FASTIO_OPERATION

FLT_IS_FS_FILTER_OPERATION

FLT_IS_IRP_OPERATION

FLT_PARAMETERS

FltWriteFile

IRP_MJ_WRITE

ZwWriteFile