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Date: Tue, 18 Feb 2025 21:02:20 +0100
To: cygwin AT cygwin DOT com
Subject: Re: [regression-3.6] df -k on Cygwin 3.6 no longer lists all
 filesystems
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Feb 18 11:41, Jeremy Drake via Cygwin wrote:
> On Tue, 18 Feb 2025, Corinna Vinschen via Cygwin wrote:
> 
> > On Feb 18 11:19, Jeremy Drake via Cygwin wrote:
> > > On Tue, 18 Feb 2025, Corinna Vinschen via Cygwin wrote:
> > >
> > > > Yep. Are you going to create a patch?
> > >
> > > I'm not seeing a particularly clean way to do this.  Bring back
> > > available_drives, mask off bits when we see the corresponding drive root
> > > from dos_drive_mappings, and return those drive letters whose bits are
> > > still set at the end?
> >
> > No, I wouldn't do that.
> >
> > IMHO, the cleanest way to bring this back is to extend
> > dos_drive_mappings::dos_drive_mappings():
> >
> > - Prior to the FindFirstVolumeW/FindNextVolumeW loop, prepend another
> >   loop iterating over GetLogicalDrives() or GetLogicalDriveStringsW().
> >   In the loop, call QueryDosDevice and add this info to
> >   dos_drive_mappings, just as in the FindVolume loop.
> >
> > - In the second loop, simply ignore all mounts mounted to just a drive
> >   letter (because the first loop already added them all).
> >
> > Makes sense?
> 
> The second loop would have to go back over the list created by the first
> loop, to see if the volume it's trying to add already has an entry, and if
> so extend its dosmount linked list with additional (non-drive-letter
> roots) mounts for that volume.  I guess it only needs to do that if there
> are any volumes which have both drive-letter-root AND
> non-drive-letter-root mounts, so that's not TOO bad.

I'm pretty sure the second loop doesn't have to do much testing.

GetLogicalDrives/GetLogicalDriveStringsW both return *all* simple drive
letter mount points valid for the current user.

So in the second loop, you can just skip all simple drive letter mount
points returned by GetVolumePathNamesForVolumeNameW, without further
testing.  They already have been returned above.  You only have
to memorize the mount points mounted on directories in this loop.

You *could* first do the FindFirstVolumeW/FindNextVolumeW loop and
*then* the GetLogicalDrives/GetLogicalDriveStringsW loop, but in this
case you really have to check every single drive letter if it already
has shown up in the first loop...

> I'll try to make a patch for this.

Great!

Thanks,
Corinna

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