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Date: Sat, 8 Feb 2025 10:18:04 +0100
To: cygwin AT cygwin DOT com
Subject: Re: exposing Windows mountpoints in Cygwin
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Feb  7 11:19, Jeremy Drake via Cygwin wrote:
> On Fri, 7 Feb 2025, Corinna Vinschen via Cygwin wrote:
> 
> > On Feb  6 13:31, Jeremy Drake via Cygwin wrote:
> > > Now that my patch to escape characters in /proc/mounts has been applied,
> > > I'll get back to what I was thinking about back in June.  I would like to
> > > have a way to list Windows volume roots in Cygwin, and it seems to make
> > > sense to me to expose them via getmntent, /proc/mounts, etc.  The way I
> > > see this working is probably to replace the available_drives mechanism for
> > > enumerating mounts in favor of using FindFirst/NextVolumeW and
> > > GetVolumePathNamesForVolumeNameW to enumerate cygdrive mount points.
> >
> > Been there, done that, but that was more than 10 years ago, so things
> > might have changed.  At the time, the volume manager was incredibly
> > slow.  Enumerating and converting volume paths from one style into the
> > other just took too much time.  And, as you know, Cygwin already is
> > slow...
> >
> > Still, if you want to do that, it should not be part of the standard
> > mount points becasue this is another level of implementation.  These are
> > the POSIX mount points handled by Cygwin.  That should be part of the
> > cygdrive handling.  Sounds like you were mulling over this anyway.
> 
> Right, the cygdrive_getmntent function in mount.cc.
> 
> > But it's not quite clear what the expected output should be.
> 
> > So what is the expected output in the cygdrive dir?
> >
> > What I could imagine is something like this.  Assuming two drives, one
> > of them mounted into a dir:
> >
> >   C:		\Device\HarddiskVolume1
> >   C:\foo	\Device\HarddiskVolume2
> >
> >   $ ls -gG /cygdrive
> >   d---r-x---+ 1  0 Feb  7 03:38 c
> >   drwxrwxr-x  1  0 Jan  8 11:02 c_foo -> /mnt/c/foo
> 
> I'm thinking much simpler than that.  I'm just thinking about enumerating
> directory mounts in the cygdrive_getmntent function.  So /cygdrive looks
> the same as it does now, just the roots of drives, but for instance mount
> would show something like
> 
> C: on /cygdrive/c type ntfs (binary,noacl,posix=0,user,noumount,auto)
> C:/foo on /cygdrive/c/foo type ntfs (binary,noacl,posix=0,user,noumount,auto)
> 
> Presumably this would also make df privy to them.

Go for it.  There's already matching logic in fhandler/proc.cc,
function format_proc_partitions() for the "win-mounts" column
of /proc/partitions.  Probably this can be reused.


Corinna

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