PFLT_POST_OPERATION_CALLBACK callback function (fltkernel.h)
A minifilter driver can register one or more routines of type PFLT_POST_OPERATION_CALLBACK to perform completion processing for I/O operations.
Syntax
PFLT_POST_OPERATION_CALLBACK PfltPostOperationCallback;
FLT_POSTOP_CALLBACK_STATUS PfltPostOperationCallback(
[in, out] PFLT_CALLBACK_DATA Data,
[in] PCFLT_RELATED_OBJECTS FltObjects,
[in, optional] PVOID CompletionContext,
[in] FLT_POST_OPERATION_FLAGS Flags
)
{...}
Parameters
[in, out] Data
A pointer to the callback data FLT_CALLBACK_DATA structure for the I/O operation.
[in] FltObjects
A pointer to a filter manager maintained FLT_RELATED_OBJECTS structure that contains opaque pointers for the objects related to the current I/O request.
[in, optional] CompletionContext
A context pointer that was returned by the minifilter driver's pre-operation callback PFLT_PRE_OPERATION_CALLBACK routine. The CompletionContext pointer provides a way to communicate information from the pre-operation callback routine to the post-operation callback routine.
[in] Flags
A bitmask of flags that specifies how the post-operation callback is to be performed.
| Flag | Meaning |
|---|---|
| FLTFL_POST_OPERATION_DRAINING | The filter manager sets this flag to indicate that the minifilter driver instance is being detached and that this post-operation callback routine is being called to clean up the minifilter driver's completion context. The post-operation callback should return FLT_POSTOP_FINISHED_PROCESSING. If this flag is set, the Data parameter points to a copy of the original callback data structure for the operation, not the original callback data structure. Additionally, when this flag is set, the post-operation callback routine is called at IRQL <= APC_LEVEL. |
Return value
This callback routine returns one of the following status values:
| Return code | Description |
|---|---|
|
The minifilter driver has finished completion processing for the I/O operation and is returning control of the operation to the filter manager.
After the post-operation callback returns this status value, the filter manager continues completion processing of the I/O operation. |
|
The minifilter driver has halted completion processing for the I/O operation, but it is not returning control of the operation to the filter manager.
A minifilter driver's post-operation callback can return this status value only if the minifilter driver's post-operation callback has posted the I/O operation to a work queue. The minifilter driver must eventually resume completion processing of the I/O operation. After the post-operation callback returns FLT_POSTOP_MORE_PROCESSING_REQUIRED, the filter manager performs no further completion processing of the I/O operation, unless both of the following conditions are true:
|
|
The minifilter driver is disallowing a fast QueryOpen operation and forcing the operation down the slow path. Doing so causes the I/O manager to service the request by performing an open/query/close of the file. Minifilter drivers should only return this status for QueryOpen. |
Remarks
A minifilter driver's post-operation callback routine performs completion processing for one or more types of I/O operations.
Post-operation callback routines are similar to the completion routines used by legacy file system filter drivers.
Post-operation callback routines are called in an arbitrary thread context, at IRQL <= DISPATCH_LEVEL. Because this callback routine can be called at IRQL DISPATCH_LEVEL, it is subject to the following constraints:
- It cannot safely call any kernel-mode routine that must run at a lower IRQL.
- Any data structures used in this routine must be allocated from nonpaged pool.
- It cannot be made pageable.
- It cannot acquire resources, mutexes, or fast mutexes. However, it can acquire spin locks.
- It cannot get, set, or delete contexts, but it can release contexts.
Any I/O completion processing that needs to be performed at IRQL < DISPATCH_LEVEL cannot be performed directly in the postoperation callback routine. Instead, it must be posted to a work queue by calling a routine such as FltDoCompletionProcessingWhenSafe or FltQueueDeferredIoWorkItem.
Be aware that FltDoCompletionProcessingWhenSafe should never be called if the Flags parameter of the post-operation callback has the FLTFL_POST_OPERATION_DRAINING bit set. The following are exceptions to this rule:
- If a minifilter driver's pre-operation callback routine returns FLT_PREOP_SYNCHRONIZE for an IRP-based I/O operation, the corresponding post-operation callback routine is guaranteed to be called at IRQL <= APC_LEVEL, in the same thread context as the pre-operation callback.
- Post-create callback routines are guaranteed to be called at IRQL PASSIVE_LEVEL, in the context of the thread that originated the IRP_MJ_CREATE operation.
A minifilter driver registers a post-operation callback routine for a particular type of I/O operation by storing the callback routine's entry point in the OperationRegistration array of the FLT_REGISTRATION structure. The minifilter driver passes this structure as a parameter to FltRegisterFilter in its DriverEntry routine.
A minifilter driver can register a post-operation callback routine for a particular type of I/O operation without registering a pre-operation callback (PFLT_PRE_OPERATION_CALLBACK) routine, and vice versa.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Available in Microsoft Windows 2000 Update Rollup 1 for SP4, Windows XP SP2, Windows Server 2003 SP1, and later Windows operating systems. |
| Target Platform | Desktop |
| Header | fltkernel.h (include FltKernel.h) |
| IRQL | See Remarks section |
See also
FltCompletePendedPostOperation