On Wed 03 Mar 2021 17:33:16 GMT Shengjing Zhu write:
>
> On Wed, Mar 3, 2021 at 3:40 PM Nicolas Schier <nicolas@fjasle.eu> wrote:
> > > [2]: https://lore.kernel.org/linux-unionfs/CAJfpegsiuf8ib5cvVrr=zHZ+Xu7BMMTT2eYapsEUdmPcRBUiwQ@mail.gmail.com/T/#t
> >
> > The overlay fs patchset [2] has been merged and with v5.10.13 (tested
> > on linux-image-5.10.0-3-arm64) the issue is no more reproducible for
> > me. Might you want to re-check on your site?
> >
>
> If I understand correctly, the upstream patch is merged into the v5.11 tree.
Sorry. Yes, you're right.
> And I still can reproduce the error on the Debian v5.10 kernel.
That confuses me quite a bit. I did it once again on an ext4 mount
(still the 5.10.0-3-arm64 kernel):
nsc@lillesand:/tmp$ cat /sys/module/overlay/parameters/permit_mounts_in_userns
Y
nsc@lillesand:/tmp$ mkdir -p test/lower/a test/merged test/upper test/work
nsc@lillesand:/tmp$ uname -a | tee test/lower/a/a
Linux lillesand 5.10.0-3-arm64 #1 SMP Debian 5.10.13-1 (2021-02-06) aarch64 GNU/Linux
nsc@lillesand:/tmp$ unshare -m -U -r
root@lillesand:/tmp# mount -t overlay -o rw,lowerdir=/tmp/test/lower,upperdir=/tmp/test/upper,workdir=/tmp/test/work overlay /tmp/test/merged
root@lillesand:/tmp# rm -rf test/merged/a
root@lillesand:/tmp# find test -ls
1597776 4 drwxr-xr-x 6 root root 4096 mars 3 08:24 test
1973978 4 drwxr-xr-x 2 root root 4096 mars 3 08:27 test/upper
2099881 0 c--------- 1 root root 0, 0 mars 3 08:27 test/upper/a
1973978 4 drwxr-xr-x 1 root root 4096 mars 3 08:27 test/merged
1714388 4 drwxr-xr-x 3 root root 4096 mars 3 08:24 test/lower
1714389 4 drwxr-xr-x 2 root root 4096 mars 3 08:27 test/lower/a
1714393 4 -rw-r--r-- 1 root root 86 mars 3 10:48 test/lower/a/a
1973979 4 drwxr-xr-x 3 root root 4096 mars 3 10:48 test/work
2099880 4 d--------- 2 root root 4096 mars 3 10:48 test/work/work
root@lillesand:/tmp#
Do you see any kernel log message from overlay fs? Might it depend on
the underlying filesystem? Can you create a white-out char dev node
manually?
> And another thing is that the upstream patch introduces a new mount
> option, userxattr, instead of module parameter.
The 'permit_mounts_in_userns' module parameter becomes superfluous with
v5.11 as overlay fs mounts will then always be enabled in userspace
namespace.
Kind regards,
Nicolas
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