FltRetainSwappedBufferMdlAddress function (fltkernel.h)
FltRetainSwappedBufferMdlAddress prevents the Filter Manager from freeing the memory descriptor list (MDL) for a buffer that was swapped in by a minifilter driver.
Syntax
void FltRetainSwappedBufferMdlAddress(
[in] PFLT_CALLBACK_DATA CallbackData
);
Parameters
[in] CallbackData
Pointer to the callback data structure for the operation.
Return value
None
Remarks
When a minifilter driver swaps in a new buffer in a preoperation callback (PFLT_PRE_OPERATION_CALLBACK) routine, the Filter Manager automatically frees the buffer's MDL when the corresponding postoperation (PFLT_POST_OPERATION_CALLBACK) callback routine returns.
The minifilter driver can prevent the Filter Manager from freeing the MDL by calling FltRetainSwappedBufferMdlAddress from the postoperation callback routine.
After calling FltRetainSwappedBufferMdlAddress, the caller is responsible for freeing the MDL by calling a routine such as IoFreeMdl.
FltRetainSwappedBufferMdlAddress can only be called from a postoperation callback routine.
Requirements
| Requirement | Value |
|---|---|
| Target Platform | Universal |
| Header | fltkernel.h (include Fltkernel.h) |
| Library | FltMgr.lib |
| DLL | Fltmgr.sys |
| IRQL | Any level |