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CBFS 5 mounts additional drive on Windows 10.

Posted: 07/06/2015 08:39:52
by Bartosz Siewior (Priority Standard support level)
Joined: 01/13/2015
Posts: 6

Hi, I found a problem with CBFS and Windows 10. I was able to reproduce the behavior using Mapper sample.

When I add network drive under letter F: and letter E: is free and when I have implemented OnGetVolumeLabel callback, CBFS adds additional drive (normal - not network) under letter E: with the same data. The result is that I have two drives with the same data (one is network, the other one isn't). On previous Windows versions the problem didn't exist. I always had only one drive even when I was settings different labels in OnGetVolumeLabel callback.

I know that you're working on driver that's gonna officially support Windows 10. I just wanted to let you know of that issue in case you weren't aware yet.
Posted: 07/06/2015 09:05:22
by Volodymyr Zinin (Team)


Is the problem reproducible with the last CBFS build (v.5.1.159)? As I remember a similar problem has been fixed there.

Posted: 07/06/2015 10:11:04
by Bartosz Siewior (Priority Standard support level)
Joined: 01/13/2015
Posts: 6

I didn't check the latest. The one I'm using right now is v.5.1.157. I was just testing my software on Windows 10 VM and this is what I discovered. I don't have possibility to test newest build right now because when I added vm's share under E: the problem disappeared. Even after I removed vm's shared from E: I wasn't able to reproduce it again... I would probably have to get fresh Windows 10 vm to check newest build.
Posted: 07/20/2015 08:55:03
by Bartosz Siewior (Priority Standard support level)
Joined: 01/13/2015
Posts: 6

Hi guys,

I've checked the latest build (5.1.160) and I wasn't able to reproduce the problem. Neither with my software nor with Mapper. I guess this is already fixed then :).
Posted: 07/20/2015 09:12:08
by Eugene Mayevski (Team)

Just for information:

a "duplicate" disk letter is not a bug at all.

Windows automatically assigns a drive letter to the newly mounted volume. There's no documented way to suppress this behavior.

What CBFS does is a call to one of internal functions of Windows kernel, which accepts certain constant as a parameter. This constant is different from version to version. So for each Windows version Volodymyr needs to dig deep into Windows kernel, find the proper value of the constant and add it to our code so that CBFS could remove the automatically assigned drive letter.

Sincerely yours
Eugene Mayevski
Posted: 03/18/2016 06:16:19
by Takhir Bedertdinov (Standard support level)
Joined: 12/11/2009
Posts: 14

I could reproduce these diplicated drives situation on Windows 10 with CBFS ONLY in the combination of g_CbFs.SetStorageType(CallbackFileSystem::stDiskPnP) set and g_CbFs.SetStorageCharacteristics((CallbackFileSystem::CbFsStorageCharacteristics)0) NOT set.
Hope this help.

Posted: 03/18/2016 06:26:05
by Eugene Mayevski (Team)

We will add this to our task list and check it when the time allows (maybe in April).

Sincerely yours
Eugene Mayevski



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