Need Solution for Error Handling in CloseFile for Remote Drive with FTP Integration

[cowboy823]

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Environment

• Windows version:
• Processor architecture:
• Dokany version:
• Library type (Dokany/FUSE):

Check List

• I checked my issue doesn't exist yet
• My issue is valid with mirror default sample and not specific to my user-mode driver implementation
• I can always reproduce the issue with the provided description below.
• I have updated Dokany to the latest version and have reboot my computer after.
• I tested one of the last snapshot from appveyor CI

Description

I'm currently developing a remote drive that functions similarly to a local drive but uses a remote directory on an FTP server. The primary function is to allow users to copy files to this drive, which internally triggers the transfer of files to the FTP server.
After the file copying process completes, I need to implement a feature that verifies if the entire file content was successfully transferred to the remote server. My initial approach is to perform this integrity check within the DokanCloseFile function.
However, I noticed that DokanCloseFile does not return a value, which poses a challenge. If an error occurs during the file close operation (e.g., the file content is not completely transferred), there's no mechanism for DokanCloseFile to report this error. Consequently, Explorer or other applications won't be able to detect the error and notify the user, such as prompting for a file retransfer.
Request:
Could you please provide guidance or a potential solution to handle this scenario? Specifically, I'm looking for a way to inform Explorer or the corresponding application that an error occurred during the close operation so that the user can be notified and take appropriate action.
Any suggestions or workarounds to solve this problem would be greatly appreciated.
Thank you for your support!

Logs

Please attach in separate files: mirror output, library logs and kernel logs.
In case of BSOD, please attach minidump or dump analyze output.

[Liryna]

Hi @cowboy823,

Close would be too late to report an error. Most apps do not even check the return value of CloseHandle.
If there is a risk that write might fail, then write should be the one returning an error. If the backend is too slow to perform write in live, I would suggest writing in a local cache and then later when there is no more activity on the file (some apps open / write / close multiple times in a row), upload the content to the backend.