ZwFlushBuffersFileEx function (ntifs.h)

Article
07/06/2023

The ZwFlushBuffersFileEx routine is called by a file system filter driver to send a flush request for a given file to the file system. An optional flush operation flag can be set to control how file data is written to storage.

Syntax

NTSYSAPI NTSTATUS ZwFlushBuffersFileEx(
  [in]  HANDLE           FileHandle,
        ULONG            FLags,
        PVOID            Parameters,
        ULONG            ParametersSize,
  [out] PIO_STATUS_BLOCK IoStatusBlock
);

Parameters

[in] FileHandle

Handle returned by ZwCreateFile or ZwOpenFile for the file whose buffers will be flushed. This parameter is required and cannot be NULL.

FLags

Flush operation flags. Flags can be 0 or one of the following values.

Value	Meaning
FLUSH_FLAGS_FILE_DATA_ONLY	If the file is on an NTFS file system, file data in the file cache will be written. No metadata is written and the underlying storage is not synchronized to flush its cache. This flag is not valid with volume handles.
FLUSH_FLAGS_NO_SYNC	If the file is on an NTFS file system, file data and metadata in the file cache will be written. The underlying storage is not synchronized to flush its cache. This flag is not valid with volume handles.

Parameters

Address of the caller's I/O status block. This parameter is required and cannot be NULL.

ParametersSize

The size, in bytes, of the parameters block.

[out] IoStatusBlock

Address of the caller's I/O status block. This parameter is required and cannot be NULL.

Return value

ZwFlushBuffersFileEx returns STATUS_SUCCESS or an appropriate NTSTATUS value, such as one of the following:

Return code	Description
STATUS_MEDIA_WRITE_PROTECTED	The file resides on a write-protected volume; this is an error code.
STATUS_VOLUME_DISMOUNTED	The file resides on a volume that is not currently mounted; this is an error code.
STATUS_ACCESS_DENIED	The file does has neither write or append access.

Remarks

A file system filter driver can call ZwFlushBuffersFileEx to issue an IRP_MJ_FLUSH_BUFFERS request to the file system for a given file. The flush operation is synchronous.

Minifilter drivers should call FltFlushBuffers instead of calling ZwFlushBuffersFileEx.

Callers of ZwFlushBuffersFileEx must be running at IRQL = PASSIVE_LEVEL and with special kernel APCs enabled.

Note If the call to the ZwFlushBuffersFileEx function occurs in user mode, you should use the name "NtFlushBuffersFileEx" instead of "ZwFlushBuffersFileEx".

For calls from kernel-mode drivers, the **Nt*Xxx*** and **Zw*Xxx*** versions of a Windows Native System Services routine can behave differently in the way that they handle and interpret input parameters. For more information about the relationship between the **Nt*Xxx*** and **Zw*Xxx*** versions of a routine, see [Using Nt and Zw Versions of the Native System Services Routines](/windows-hardware/drivers/kernel/using-nt-and-zw-versions-of-the-native-system-services-routines).

Requirements

Requirement	Value
Minimum supported client	Windows 8.
Target Platform	Universal
Header	ntifs.h (include Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	PASSIVE_LEVEL (See Remarks section.)