From: Christian Brauner <christian.brauner@ubuntu.com>
To: Christian Kellner <christian@kellner.me>
Cc: jannh@google.com, aarcange@redhat.com, akpm@linux-foundation.org,
cyphar@cyphar.com, elena.reshetova@intel.com, guro@fb.com,
ldv@altlinux.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org, mhocko@suse.com, mingo@kernel.org,
peterz@infradead.org, tglx@linutronix.de,
viro@zeniv.linux.org.uk
Subject: Re: [PATCH] pidfd: add NSpid entries to fdinfo
Date: Mon, 14 Oct 2019 12:31:58 +0200 [thread overview]
Message-ID: <20191014103157.h2wph2ujjidsrhyw@wittgenstein> (raw)
In-Reply-To: <abc477fb3bd8fbf7b4d7e53d079dd1d8902e54af.camel@kellner.me>
On Mon, Oct 14, 2019 at 11:43:01AM +0200, Christian Kellner wrote:
> On Sat, 2019-10-12 at 12:21 +0200, Christian Brauner wrote:
> > I think this might be more what we want.
> Yep, indeed.
>
> > I tried to think of cases where the first entry of Pid is not
> > identical
> > to the first entry of NSpid but I came up with none. Maybe you do,
> > Jann?
> Yeah, I don't think that can be the case. By looking at the source of
> 'pid_nr_ns(pid, ns)' a non-zero return means that a) 'pid' valid, ie.
> non-null and b) 'ns' is in the pid namespace hierarchy of 'pid' (at
> pid->level, i.e. "pid->numbers[ns->level].ns == ns").
>
> > Christian, this is just a quick stab I took. Feel free to pick this
> > up as a template.
> Thanks! I slightly re-worked it, with the reasoning above in mind, to
> get rid of one of the branches:
Thanks!
>
> +#ifdef CONFIG_PID_NS
> + seq_put_decimal_ull(m, "\nNSpid:\t", nr);
> + if (nr) {
> + int i;
> +
> + /* If nr is non-zero it means that 'pid' is valid and that
> + * ns, i.e. the pid namespace associated with the procfs
> + * instance, is in the pid namespace hierarchy of pid.
> + * Start at one level below and print all descending pids.
> + */
> + for (i = ns->level + 1; i <= pid->level; i++) {
> + ns = pid->numbers[i].ns;
I'm not a fan of overriding the "ns" pointer. It's not a huge deal but
it's rather subtle.
> + seq_put_decimal_ull(m, "\t", pid_nr_ns(pid, ns));
> + }
> + }
> +#endif
>
> But I now just realized that with the very same reasoning, if nr is
> non-zero, we don't need to redo all the checks and can just do:
>
> for (i = ns->level + 1; i <= pid->level; i++)
> seq_put_decimal_ull(m, "\t", pid->numbers[i].nr);
>
> If this sounds good to you I resend the patches with the change above.
You could probably do:
#ifdef CONFIG_PID_NS
seq_put_decimal_ull(m, "\nNSpid:\t", nr);
for (i = ns->level + 1; i <= pid->level && nr; i++)
seq_put_decimal_ull(m, "\t", pid->numbers[i].nr);
#endif
Christian
next prev parent reply other threads:[~2019-10-14 10:32 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 13:36 [PATCH] pidfd: show pids for nested pid namespaces in fdinfo Christian Kellner
2019-10-08 13:52 ` Christian Brauner
2019-10-08 14:00 ` Michal Hocko
2019-10-09 16:05 ` [PATCH v2 1/2] " Christian Kellner
2019-10-09 16:05 ` [PATCH v2 2/2] pidfd: add tests for NSpid info " Christian Kellner
2019-10-11 15:09 ` Jann Horn
2019-10-11 17:08 ` Christian Brauner
2019-10-09 17:29 ` [PATCH v2 1/2] pidfd: show pids for nested pid namespaces " Christian Brauner
2019-10-11 12:23 ` [PATCH v3 " Christian Kellner
2019-10-11 12:23 ` [PATCH v3 2/2] pidfd: add tests for NSpid info " Christian Kellner
2019-10-11 13:18 ` Christian Brauner
2019-10-11 13:17 ` [PATCH v3 1/2] pidfd: show pids for nested pid namespaces " Christian Brauner
2019-10-11 14:55 ` Jann Horn
2019-10-11 15:17 ` Christian Brauner
2019-10-11 15:30 ` Jann Horn
2019-10-11 16:58 ` Christian Brauner
2019-10-11 18:20 ` Jann Horn
2019-10-12 10:19 ` [PATCH] pidfd: add NSpid entries to fdinfo Christian Brauner
2019-10-12 10:21 ` Christian Brauner
2019-10-14 9:43 ` Christian Kellner
2019-10-14 10:31 ` Christian Brauner [this message]
2019-10-14 15:10 ` Jann Horn
2019-10-14 15:20 ` Christian Kellner
2019-10-14 15:09 ` Jann Horn
2019-10-14 17:06 ` Christian Brauner
2019-10-14 16:20 ` [PATCH v4 1/2] " Christian Kellner
2019-10-14 16:20 ` [PATCH v4 2/2] pidfd: add tests for NSpid info in fdinfo Christian Kellner
2019-10-15 10:07 ` Christian Brauner
2019-11-13 11:52 ` Naresh Kamboju
2019-11-13 12:20 ` Christian Brauner
2019-10-15 9:40 ` [PATCH v4 1/2] pidfd: add NSpid entries to fdinfo Christian Brauner
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