[regression-3.6] coreutils mkdir broken on UNC paths

Thu Feb 20 20:36:37 GMT 2025

On Feb 20 19:24, Lionel Cons via Cygwin wrote:
> On 2025年2月20日 at 18:09, Corinna Vinschen via Cygwin
> <cygwin@cygwin.com> wrote:
> >
> > On Feb 20 17:37, Lionel Cons via Cygwin wrote:
> > > On 2025年2月20日 at 14:56, Cedric Blancher via Cygwin
> > > <cygwin@cygwin.com> wrote:
> > > >
> > > > Good afternoon!
> > > >
> > > > Cygwin 3.6.0-0.378.g78fb13d21f4f.x86_64, Cygwin coreutils package 9.6-1
> > > >
> > > > coreutils mkdir is broken on UNC paths:
> > > >
> > > > mkdir -p -- "//ember.data4.local/afs/disk11/builds/bash/install_root/usr/local/bin"
> > > > mkdir: cannot create directory ‘//ember.data4.local’: Read-only file system
> > > >
> > > > This happens because you cannot do a "cd .." in
> > > > //ember.data4.local/afs, because "afs" is the UNC prefix for that
> > > > filesystem.
> > >
> > > No, it happens because mkdir "//ember.data4.local" returns "Read-only
> > > file system". If Cygwin would just return EEXIST if this mount exists,
> > > then this whole mkdir -p would work.
> >
> > You know exactly what Cygwin is doing wrong, great!
>> Sorry, it has been a very long day, and I did not communicate my point
> precisely.
> My point is that mkdir("//ember.data4.local") for a share should in my
> opinion not return EROFS, because the share already exists.
>> Looking at the code:
> int
> fhandler_base::mkdir (mode_t)
> {
> if (exists ())
> set_errno (EEXIST);
> else
> set_errno (EROFS);
> return -1;
> }
>> My guess is that exists() fails. The why? and how? I do not know.

And here's the problem. It works fine for me on all shares, be it SMB,
Samba, or NFS:
https://cygwin.com/pipermail/cygwin/2025-February/257438.html
> Maybe the hostname resolution in fhandler_netdrive::exists() failed?

If so, it would be a problem on your side.
Does `nslookup ember.data4.local' return a valid address?
I just pushed a patch to print a debug statement in strace output
to see what error code GetAddrInfoW returned.
The next test release cygwin-3.6.0-0.380-gdf307349a09e, due in an hour
or so, will contain that patch. Rerun mkdir as above under strace and
send the full trace output as attachment.
Corinna