Re: [LTP] [PATCH] ioctl_pidfd02-06: Add CONFIG_USER_NS and CONFIG_PID_NS to needs_kconfigs

Andrea Cervesato via ltp
2025-12-18T08:19:13Z

Hi,

On Mon Dec 15, 2025 at 5:52 PM CET, Petr Vorel wrote:
> > > And https://www.man7.org/linux/man-pages/man7/user_namespaces.7.html.
>
> > > Yeah, I understand that. The dependency of CLONE_NEWUSER/CLONE_NEWPID is also
> > > visible in kernel sources (e.g. fs/nsfs.c). But my question was different:
> > > Do we now prefer everything kind of document with .needs_kconfigs, even it's
> > > possible to detect it otherwise? (speed of parsing kconfig, kind of hard request
> > > for kconfig being available even we can figure the support otherwise).
>
> > I believe we shouldn't see this as black/white but use this feature when
> > it's really needed. This is the case.
>
> Sure, .needs_kconfigs is used when test request some functionality based on
> kconfig. But many tests use /proc or /sys based detection (e.g. ioctl_ns06.c)
> or based on certain errno, see include/lapi/syscalls.h or
> testcases/kernel/syscalls/fanotify/fanotify.h) because these were
> added before LTP supported kconfig. Later, when kconfig was added it was
> considering as a last resort (when there was no way to detect dependency
> otherwise).
>
> Have we decide to move everything into kconfig?
>
> I'm not sure myself. needs_kconfigs is simpler and obvious, but it requires
> kernel config. I suppose the speed of parsing config is not an issue.
>
> It'd be nice to mention the resolution (preferred vs. only if no other way to
> detect the support) into
> https://linux-test-project.readthedocs.io/en/latest/developers/writing_tests.html

Feel free to add this comment, but for me it's obvious that if a
feature can't be present in the kernel due to kconfigs we should check
kconfig :-)

>
> or into upcommig doc/developers/ground_rules.rst
> https://patchwork.ozlabs.org/project/ltp/patch/20251215124404.16395-2-chrubis@suse.cz/
>
> Kind regards,
> Petr
>
> > > And if we decide for forcing kconfig, we should update ioctl_ns06.c, which does
> > > /proc based detection (i.e. to use the same approach).
>
> > I didn't check this, but I'm pretty sure we should go all around and
> > verify many other tests with the same issue. We should do it in this
> > patch-set or on a searate one.
>
>
> > > Kind regards,
> > > Petr

So what we do with the patch? Should we merge it?

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com