netdev - Re: [PATCH] bpf/selftests: Fix namespace mount setup in tc

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Date:   Tue, 18 Jan 2022 19:48:52 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Jussi Maki <joamaki@...il.com>, Hangbin Liu <haliu@...hat.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH] bpf/selftests: Fix namespace mount setup in tc_redirect

On Mon, Jan 17, 2022 at 11:25 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Thu, Jan 06, 2022 at 08:35:18AM +0100, Jiri Olsa wrote:
> > On Wed, Jan 05, 2022 at 12:40:34PM -0800, Andrii Nakryiko wrote:
> > > On Tue, Jan 4, 2022 at 4:10 AM Jiri Olsa <jolsa@...hat.com> wrote:
> > > >
> > > > The tc_redirect umounts /sys in the new namespace, which can be
> > > > mounted as shared and cause global umount. The lazy umount also
> > > > takes down mounted trees under /sys like debugfs, which won't be
> > > > available after sysfs mounts again and could cause fails in other
> > > > tests.
> > > >
> > > >   # cat /proc/self/mountinfo | grep debugfs
> > > >   34 23 0:7 / /sys/kernel/debug rw,nosuid,nodev,noexec,relatime shared:14 - debugfs debugfs rw
> > > >   # cat /proc/self/mountinfo | grep sysfs
> > > >   23 86 0:22 / /sys rw,nosuid,nodev,noexec,relatime shared:2 - sysfs sysfs rw
> > > >   # mount | grep debugfs
> > > >   debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
> > > >
> > > >   # ./test_progs -t tc_redirect
> > > >   #164 tc_redirect:OK
> > > >   Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED
> > > >
> > > >   # mount | grep debugfs
> > > >   # cat /proc/self/mountinfo | grep debugfs
> > > >   # cat /proc/self/mountinfo | grep sysfs
> > > >   25 86 0:22 / /sys rw,relatime shared:2 - sysfs sysfs rw
> > > >
> > > > Making the sysfs private under the new namespace so the umount won't
> > > > trigger the global sysfs umount.
> > >
> > > Hey Jiri,
> > >
> > > Thanks for the fix. Did you try making tc_redirect non-serial again
> > > (s/serial_test_tc_redirect/test_tc_redirect/) and doing parallelized
> > > test_progs run (./test_progs -j) in a tight loop for a while? I
> > > suspect this might have been an issue forcing us to make this test
> > > serial in the first place, so now that it's fixed, we can make
> > > parallel test_progs a bit faster.
> >
> > hi,
> > right, will try
>
> so I can't reproduce the issue in the first place - that means without my
> fix and with reverted serial_test_tc_redirect change - by running parallelized
> test_progs, could you guys try it?
>

I tried it for a bunch of iterations and didn't repro it either.
Doesn't mean much as CI's environment is different, but I think it
might be worth making it parallel again and see if it reproes in CI
again.

> jirka
>