Failing an I/O Operation in a Postoperation Callback Routine

A minifilter driver's postoperation callback routine can fail a successful I/O operation, but simply failing an I/O operation does not undo the effect of the operation. The minifilter driver is responsible for performing any processing that is needed to undo the operation.

For example, a minifilter driver's post-create callback routine can fail a successful IRP_MJ_CREATE operation by performing the following steps:

  1. Calling FltCancelFileOpen to close the file that was created or opened by the create operation. Note that FltCancelFileOpen does not undo any modifications to the file. For example, FltCancelFileOpen does not delete a newly created file or restore a truncated file to its previous size.

  2. Setting the callback data structure's IoStatus.Status field to the final NTSTATUS value for the operation. This value must be a valid error NTSTATUS value, such as STATUS_ACCESS_DENIED.

  3. Setting the callback data structure's IoStatus.Information field to zero.

  4. Returning FLT_POSTOP_FINISHED_PROCESSING.

When setting the callback data structure's IoStatus.Status field to the final NTSTATUS value for the operation, the minifilter driver must specify a valid error NTSTATUS value. Note that minifilter drivers cannot specify STATUS_FLT_DISALLOW_FAST_IO; only the filter manager can use this NTSTATUS value.

Callers of FltCancelFileOpen must be running at IRQL <= APC_LEVEL. However, a minifilter driver can safely call this routine from a post-create callback routine, because, for IRP_MJ_CREATE operations, the postoperation callback routine is called at IRQL = PASSIVE_LEVEL, in the context of the thread that originated the create operation.

 

 

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