Bug#1049885: overlayfs: cannot rename symlink if lower filesystem is NFS

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + moreinfo

Hi Guido,

On Wed, Aug 16, 2023 at 03:34:45PM +0200, Guido Berhoerster wrote:
> Package: linux-image-6.1.0-10-amd64
> Version: 6.1.38-2
> 
> rename(2) on a symlink on an overlayfs where the lower filesystem is NFS
> fails with ENXIO.
> 
> It can be reproduced as follows:
> 
> lower=/nfs/lower # /nfs should be an nfs mount
> mkdir -p "${lower}" /upper /work /merged
> touch "${lower}"/foo
> ln -s foo "${lower}"/bar
> mount -t overlay overlay -o lowerdir="${lower}",upperdir=/upper,workdir=/work /merged
> mv /merged/bar /merged/baz
> 
> If $lower is e.g. ext4 this works.  This is a regression over kernel 
> 5.10 in bullseye. It affects ltsp causing booting into root fs on NFS 
> to fail due to an initrd script which temporarily renames the /sbin/init
> symlink, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1049397

Did you check, does that affect current stable versions upstream or
mainline?

Were you able to bisect the breaking change?

In both cases, it would be great it you can report this upstream and
keep us in the loop.

Regards,
Salvatore