FsRtlOplockFsctrl function (ntifs.h)

Article
10/21/2021

FsRtlOplockFsctrl performs various opportunistic lock (oplock) operations on behalf of a file system or filter driver.

Syntax

NTSTATUS FsRtlOplockFsctrl(
  [in] POPLOCK Oplock,
  [in] PIRP    Irp,
  [in] ULONG   OpenCount
);

Parameters

[in] Oplock

Opaque oplock pointer for the file. This pointer must have been initialized by a previous call to FsRtlInitializeOplock.

[in] Irp

Pointer to the IRP for the I/O operation. This parameter is required and cannot be NULL.

[in] OpenCount

Number of user handles for the file, if an exclusive oplock is being requested. Setting a nonzero value for a level 2, R, or RH oplock request indicates that there are byte-range locks on the file. For information about oplock types, see Oplock Overview.

Return value

FsRtlOplockFsctrl returns one of the following NTSTATUS values:

Return code	Description
STATUS_SUCCESS	For an IRP_MJ_CREATE request, STATUS_SUCCESS indicates that the requested filter oplock was granted. For a FSCTL operation, the meaning of STATUS_SUCCESS depends on the FSCTL code. For more information, see the reference pages for the FSCTL codes listed in the following Remarks section.
STATUS_CANCELLED	The I/O operation was canceled. STATUS_CANCELLED is an error code.
STATUS_INVALID_PARAMETER	The FSCTL code for the I/O operation was not one of the valid values listed in the following Remarks section. STATUS_INVALID_PARAMETER is an error code.
STATUS_OPLOCK_NOT_GRANTED	The oplock could not be granted. STATUS_OPLOCK_NOT_GRANTED is an error code.
STATUS_PENDING	Used only for FSCTL operations. The meaning of STATUS_PENDING depends on the FSCTL code. For more information, see the reference pages for the FSCTL codes listed in the following Remarks section. STATUS_PENDING is a success code.
STATUS_CANNOT_BREAK_OPLOCK	A new oplock could not be granted. The IRP is an IRP_MJ_CREATE request and FILE_OPEN_REQUIRING_OPLOCK was specified in the create options parameter for the operation. STATUS_CANNOT_BREAK_OPLOCK is a success code.

Remarks

File systems and legacy filter drivers call FsRtlOplockFsctrl to perform various oplock operations for a create or file system control I/O operation. Minifilters should call FltOplockFsctrl instead of FsRtlOplockFsctrl.

The IRP pointed to by the Irp parameter must be a valid IRP for an IRP_MJ_FILE_SYSTEM_CONTROL or IRP_MJ_CREATE operation.

If the IRP is an IRP_MJ_FILE_SYSTEM_CONTROL request, FsRtlOplockFsctrl can be used with one of the following FSCTL codes, which is set in IrpSp->Parameters.FileSystemControl.FsControlCode:

For detailed information about these FSCTLs and about opportunistic locks in general, see the Microsoft Windows SDK documentation.

If the IRP is an IRP_MJ_CREATE request, FsRtlOplockFsctrl can be used to request a pending filter oplock if all of the following conditions are true:

The value of the OpenCount parameter must be 1.
The value of the DesiredAccess parameter for the IRP_MJ_CREATE request must be FILE_READ_ATTRIBUTES.
The value of the ShareAccess parameter for the IRP_MJ_CREATE request must be FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE.

If the request for a pending filter oplock is granted, FsRtlOplockFsctrl returns STATUS_SUCCESS. For more information about create parameters, see the reference entry for IRP_MJ_CREATE.

Filters and file systems that call this function must synchronize calls into the system-supplied oplock package. See Oplock synchronization for more information.

Requirements

Requirement	Value
Target Platform	Universal
Header	ntifs.h (include Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	<= APC_LEVEL