FsRtlCheckOplock function (ntifs.h)

Article
09/27/2023

The FsRtlCheckOplock routine synchronizes the IRP for a file I/O operation with the file's current opportunistic lock (oplock) state.

Syntax

NTSTATUS FsRtlCheckOplock(
  [in]           POPLOCK                       Oplock,
  [in]           PIRP                          Irp,
  [in, optional] PVOID                         Context,
  [in, optional] POPLOCK_WAIT_COMPLETE_ROUTINE CompletionRoutine,
  [in, optional] POPLOCK_FS_PREPOST_IRP        PostIrpRoutine
);

Parameters

[in] Oplock

An opaque opportunistic lock pointer for the file. This pointer must have been initialized by a previous call to FsRtlInitializeOplock.

[in] Irp

A pointer to the IRP for the I/O operation.

[in, optional] Context

A pointer to caller-defined context information to be passed to the callback routines that the CompletionRoutine and PostIrpRoutine parameters point to.

[in, optional] CompletionRoutine

A pointer to a caller-supplied callback routine. If an opportunistic lock break is in progress, this routine is called when the break is completed. This parameter is optional and can be NULL. If it is NULL, the caller is put into a wait state until the opportunistic lock break is completed.

This routine is declared as follows:

typedef VOID
(*POPLOCK_WAIT_COMPLETE_ROUTINE) (
      IN PVOID Context,
      IN PIRP Irp
      );

This routine has the following parameters:

Parameter	Description
Context	A context information pointer that was passed in the Context parameter to FsRtlCheckOplock.
Irp	A pointer to the IRP for the I/O operation.

[in, optional] PostIrpRoutine

A pointer to a caller-supplied callback routine to be called if the I/O operation is posted to a work queue. This parameter is optional and can be NULL.

This routine is declared as follows:

typedef VOID
(*POPLOCK_FS_PREPOST_IRP) (
      IN PVOID Context,
      IN PIRP Irp
      );

This routine has the following parameters:

Parameter	Description
Context	A context information pointer that was passed in the Context parameter to FsRtlCheckOplock.
Irp	A pointer to the IRP for the I/O operation.

Return value

The FsRtlCheckOplock routine returns STATUS_SUCCESS or an appropriate NTSTATUS code such as one of the following:

Return code	Description
STATUS_CANCELLED	The IRP was canceled. STATUS_CANCELLED is an error code.
STATUS_CANNOT_BREAK_OPLOCK	If the IRP is an IRP_MJ_CREATE and FILE_OPEN_REQUIRING_OPLOCK is in the IRP's CreateOptions, the routine will not initiate a break of an existing opportunistic lock, but fails with STATUS_CANNOT_BREAK_OPLOCK.
STATUS_OPLOCK_BREAK_IN_PROGRESS	An opportunistic lock break is underway. The IRP is an IRP_MJ_CREATE request, and FILE_COMPLETE_IF_OPLOCKED was specified in the create options parameter for the operation. STATUS_OPLOCK_BREAK_IN_PROGRESS is a success code.
STATUS_PENDING	An opportunistic lock break has been initiated, and control of the IRP has been passed to the oplock package. If CompletionRoutine is NULL, this routine will block while the oplock break is processed, rather than return STATUS_PENDING. STATUS_PENDING is a success code.

Remarks

FsRtlCheckOplock synchronizes the IRP for an I/O operation with the current opportunistic lock state of a file according to the following conditions:

If the I/O operation will cause the opportunistic lock to break, the opportunistic lock break is initiated.
If the I/O operation cannot continue until the opportunistic lock break is complete, FsRtlCheckOplock returns STATUS_PENDING and calls the callback routine that the PostIrpRoutine parameter points to.

If a file system or filter driver uses opportunistic locks, it must call FsRtlCheckOplock from any dispatch routines for I/O operations that can cause opportunistic lock breaks. This rule applies to the following types of I/O operations, because these operations can cause opportunistic lock breaks:

IRP_MJ_CLEANUP
IRP_MJ_CREATE
IRP_MJ_FILE_SYSTEM_CONTROL
IRP_MJ_FLUSH_BUFFERS
IRP_MJ_LOCK_CONTROL
IRP_MJ_READ
IRP_MJ_SET_INFORMATION
IRP_MJ_WRITE

For detailed information about opportunistic locks, see the Windows SDK documentation.

Minifilters should call FltCheckOplock instead of FsRtlCheckOplock.

Requirements

Requirement	Value
Minimum supported client	Windows 2000
Target Platform	Universal
Header	ntifs.h (include FltKernel.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	<= APC_LEVEL