HRESULT 0x001F0001 (ERROR_FLT_IO_COMPLETE): meaning and diagnosis

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A lower minifilter completed callback data before the initiated Filter Manager I/O reached the file system.

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WER_S_REPORT_UPLOADED_CAB	WCM_S_INTERNALERROR

ERROR_FLT_IO_COMPLETE

The I/O already has a final result

ERROR_FLT_IO_COMPLETE is the Win32 mapping of STATUS_FLT_IO_COMPLETE. It can be returned by FltPerformAsynchronousIo or related Filter Manager paths when a minifilter instance below the initiator completes the operation in its pre-operation callback. The request therefore did not continue to the file system, but it was not merely cancelled or left pending.

The result should be interpreted together with CallbackData->IoStatus. That structure contains the final status and information value chosen by the completing filter. Reissuing the operation blindly can repeat a deliberate policy decision, and treating this status as ordinary success can discard the actual failure stored in the callback data.

What the initiating filter should preserve

Inspect the final IoStatus.Status and IoStatus.Information rather than replacing them with the wrapper status.
Keep the completion callback safe even when the operation finishes synchronously before FltPerformAsynchronousIo returns.
Distinguish a lower filter completing the request from the file system completing it normally.
Avoid an automatic retry unless the lower filter’s policy or the request parameters have changed.

References

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