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FsRtlRegisterFileSystemFilterCallbacks routine

File system filter drivers and file systems call the FsRtlRegisterFileSystemFilterCallbacks routine to register notification callback routines to be invoked when the underlying file system performs certain operations.

Syntax


NTSTATUS FsRtlRegisterFileSystemFilterCallbacks(
  _In_  struct _DRIVER_OBJECT *FilterDriverObject,
  _In_  PFS_FILTER_CALLBACKS Callbacks
);

Parameters

FilterDriverObject [in]

A pointer to the driver object for the filter or file system driver.

Callbacks [in]

A pointer to a structure that contains the entry points of caller-supplied notification callback routines.

This structure is defined as follows.

Note  All of the callback entry points are optional and can be NULL.


typedef struct _FS_FILTER_CALLBACKS {
    ULONG SizeOfFsFilterCallbacks;
    ULONG Reserved;
    PFS_FILTER_CALLBACK PreAcquireForSectionSynchronization;
    PFS_FILTER_COMPLETION_CALLBACK PostAcquireForSectionSynchronization;
    PFS_FILTER_CALLBACK PreReleaseForSectionSynchronization;
    PFS_FILTER_COMPLETION_CALLBACK PostReleaseForSectionSynchronization;
    PFS_FILTER_CALLBACK PreAcquireForCcFlush;
    PFS_FILTER_COMPLETION_CALLBACK PostAcquireForCcFlush;
    PFS_FILTER_CALLBACK PreReleaseForCcFlush;
    PFS_FILTER_COMPLETION_CALLBACK PostReleaseForCcFlush;
    PFS_FILTER_CALLBACK PreAcquireForModifiedPageWriter;
    PFS_FILTER_COMPLETION_CALLBACK PostAcquireForModifiedPageWriter;
    PFS_FILTER_CALLBACK PreReleaseForModifiedPageWriter;
    PFS_FILTER_COMPLETION_CALLBACK PostReleaseForModifiedPageWriter;
} FS_FILTER_CALLBACKS, *PFS_FILTER_CALLBACKS;

The filter callback routine and its parameters are defined as follows:


typedef
NTSTATUS (*PFS_FILTER_CALLBACK) (
              IN PFS_FILTER_CALLBACK_DATA Data,
              OUT PVOID *CompletionContext
              );

ParameterMeaning

Data

Pointer to the callback data structure for this operation.

CompletionContext

Context information to be passed to the filter completion callback routine. Set to NULL if no context information is to be passed or if there is no corresponding filter completion callback routine.

 

The filter completion callback routine and its parameters are defined as follows:


typedef
VOID (*PFS_FILTER_COMPLETION_CALLBACK) (
          IN PFS_FILTER_CALLBACK_DATA Data,
          IN NTSTATUS OperationStatus,
          IN PVOID CompletionContext
          );

ParameterMeaning

Data

Pointer to the callback data structure for this operation.

OperationStatus

Status of the operation. If the file system successfully performed the operation, this parameter is set to STATUS_SUCCESS. Otherwise, it is set to an appropriate error status value.

CompletionContext

Context information that was set in the filter callback routine. This is set to NULL if no information is passed or if there is no corresponding filter callback routine.

 

The callback data structure and its members are defined as follows:


typedef struct _FS_FILTER_CALLBACK_DATA {
    ULONG SizeOfFsFilterCallbackData;
    UCHAR Operation;
    UCHAR Reserved;
    struct _DEVICE_OBJECT *DeviceObject;
    struct _FILE_OBJECT *FileObject;
    FS_FILTER_PARAMETERS Parameters;
} FS_FILTER_CALLBACK_DATA, *PFS_FILTER_CALLBACK_DATA;

MemberMeaning

SizeOfFsFilterCallbackData

Size of the callback data structure.

Operation

File system operation for which the callback routine is to be invoked. This operation can be one of the following:

  • FS_FILTER_ACQUIRE_FOR_SECTION_SYNCHRONIZATION
  • FS_FILTER_RELEASE_FOR_SECTION_SYNCHRONIZATION
  • FS_FILTER_ACQUIRE_FOR_MOD_WRITE
  • FS_FILTER_RELEASE_FOR_MOD_WRITE
  • FS_FILTER_ACQUIRE_FOR_CC_FLUSH
  • FS_FILTER_RELEASE_FOR_CC_FLUSH

Reserved

Reserved for system use.

DeviceObject

Device object for this operation.

FileObject

File object for this operation.

Parameters

Union containing any operation-specific parameters.

 

The filter parameter union is defined as follows:


typedef union _FS_FILTER_PARAMETERS {
    struct {
        PLARGE_INTEGER EndingOffset;
        PERESOURCE *ResourceToRelease;
    } AcquireForModifiedPageWriter;
    struct {
        PERESOURCE ResourceToRelease;
    } ReleaseForModifiedPageWriter;
    struct {
 FS_FILTER_SECTION_SYNC_TYPE SyncType;
 ULONG PageProtection;
    } AcquireForSectionSynchronization;
    struct {
        PVOID Argument1;
        PVOID Argument2;
        PVOID Argument3;
        PVOID Argument4;
        PVOID Argument5;
    } Others;
} FS_FILTER_PARAMETERS, *PFS_FILTER_PARAMETERS;

ParameterMeaning

EndingOffset

Offset of the last byte being written plus one.

ResourceToRelease

Resource to be released. This parameter must not have a NULL value.

SyncType

Type of synchronization requested for the section: SyncTypeCreateSection if a section is being created, SyncTypeOther otherwise.

PageProtection

Type of page protection requested for the section. Must be zero if SyncType is SyncTypeOther. Otherwise, one of the following flags, possibly ORed with PAGE_NOCACHE:

  • PAGE_READONLY
  • PAGE_READWRITE
  • PAGE_WRITECOPY
  • PAGE_EXECUTE

Argument1

Reserved for future use.

Argument2

Reserved for future use.

Argument3

Reserved for future use.

Argument4

Reserved for future use.

Argument5

Reserved for future use.

 

Return value

The FsRtlRegisterFileSystemFilterCallbacks routine can return one of the following status values:

Return codeDescription
STATUS_SUCCESS

The callback routines were successfully registered.

STATUS_INSUFFICIENT_RESOURCES

FsRtlRegisterFileSystemFilterCallbacks encountered a pool allocation failure when allocating memory to store the callback information.

STATUS_INVALID_PARAMETER

One of the parameters is invalid.

 

Remarks

File system and file system filter drivers should call FsRtlRegisterFileSystemFilterCallbacks from the driver's DriverEntry routine.

File systems call FsRtlRegisterFileSystemFilterCallbacks to set the PreAcquireForSectionSynchronization callback member of the FS_FILTER_CALLBACKS structure instead of using the obsolete AcquireFileForNtCreateSection.

FsRtlRegisterFileSystemFilterCallbacks registers the notification callback routines that were specified in the Callbacks parameter to be invoked when requests for certain file operations are sent to the underlying file system.

Callback routines are currently defined for the following operations:

OperationNotification Callback Routine and Callback Completion Routine

The memory manager acquires a file exclusively before creating a memory-mapped section for a portion of the file.

Note  For this operation, SyncType is set to SyncTypeCreateSection.

PreAcquireForSectionSynchronization
PostAcquireForSectionSynchronization

The memory manager releases a file after creating a memory-mapped section for a portion of the file.

PreReleaseForSectionSynchronization
PostReleaseForSectionSynchronization

A kernel component (such as the cache manager) acquires a file exclusively before temporarily disabling section creation for a portion of the file.

Note  For this operation, SyncType is set to SyncTypeOther.

PreAcquireForSectionSynchronization
PostAcquireForSectionSynchronization

Note  PreAcquireForSectionSynchronization should always return a success status code (such as STATUS_SUCCESS) for this operation. Returning any other type of status code causes the system to ASSERT on a checked build. (On free builds, the status code is ignored.)

A kernel component (such as the cache manager) releases a file after temporarily disabling section creation for a portion of the file.

PreReleaseForSectionSynchronization
PostReleaseForSectionSynchronization

The cache manager acquires a file exclusively before flushing a portion of the file from the cache.

PreAcquireForCcFlush
PostAcquireForCcFlush

The cache manager releases a file after flushing a portion of the file from the cache.

PreReleaseForCcFlush
PostReleaseForCcFlush

The modified page writer acquires a file exclusively before writing a portion of the file to disk.

PreAcquireForModifiedPageWriter
PostAcquireForModifiedPageWriter

The modified page writer releases a file after writing a portion of the file to disk.

PreReleaseForModifiedPageWriter
PostReleaseForModifiedPageWriter

 

The filter notification callback routine is invoked before the operation request is passed to lower-level filter drivers and the underlying file system. In the callback routine, the filter driver should perform any needed processing and immediately return STATUS_SUCCESS. If a filter driver's callback routine returns a status value other than STATUS_SUCCESS, this causes the operation request to fail. Repeated failure of certain requests, such as locking requests, can halt system progress. Thus, filter drivers should fail such a request only when absolutely necessary. When failing these requests, the filter driver should return an error status value that describes the error as completely and accurately as possible.

Note   A filter driver's notification callback routine cannot fail a request to release a file system resource. If a filter driver returns a status value other than STATUS_SUCCESS from any of the following notification callback routines, the status value is ignored.

  • PreReleaseForSectionSynchronization

  • PreReleaseForCcFlush

  • PreReleaseForModifiedPageWriter

The filter completion callback routine is invoked after the operation request is passed to lower-level filter drivers and the underlying file system. In the completion callback routine, the filter driver must perform any needed processing and immediately return.

The callback routines defined by FsRtlRegisterFileSystemFilterCallbacks supersede the following fast I/O callback routines, which are obsolete and should not be used by file system filter drivers:

  • AcquireForCcFlush

  • AcquireFileForNtCreateSection

  • AcquireForModWrite

  • ReleaseForCcFlush

  • ReleaseFileForNtCreateSection

  • ReleaseForModWrite

Requirements

Version

This routine is available on Microsoft Windows XP and later versions of the Windows operating system.

Header

Ntifs.h (include Ntifs.h)

Library

Ntoskrnl.lib

IRQL

PASSIVE_LEVEL

 

 

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