How to detect operational failure during Close.

[ai ou]

Hello, thank you for providing such wonderful software.

I am developing an application to operate files on remote storage, using the passthrough.c source code as a reference.

Since random access to files is required, I retrieve the file at the execution of Open in FSP_FILE_SYSTEM_INTERFACE. The Read and Write operations are performed on the retrieved file, and I intend to update the remote storage upon Close.

However, since Close is defined as void without a return value, it is not possible to notify WinFsp of a failure in updating the storage. In such a case, is there a way for application users to recognize the update failure?

[Bill Zissimopoulos]

Unfortunately no, there is no way to report such an error to the user. This is because the return code from the Cleanup and Close operations (which happen after a file is closed) is ignored.

 

This may look like a problem in the Windows file system, but I note that it is a problem with Linux FUSE as well. Linux FUSE includes a flush operation that can report an error, but this operation is not invoked in the case of memory mapped files.

 

Some of my file systems have a similar design to yours, where the remote storage gets updated some time after the last CLOSE (e.g. 30 seconds). In such cases I build my remote storage update process to be resilient in the face of network outages, errors, etc. At a minimum the updates are retried and will be retried even if the file system process dies or is killed.

 

Thanks.

 

Bill

 

 

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