Re: clone3: allow creation of time namespace with offset

From: Arnd Bergmann <arnd@arndb.de>
To: Adrian Reber <areber@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Pavel Emelyanov <ovzxemul@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Andrei Vagin <avagin@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Radostin Stoyanov <rstoyanov1@gmail.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Aleksa Sarai <cyphar@cyphar.com>,
	Linux API <linux-api@vger.kernel.org>
Subject: Re: clone3: allow creation of time namespace with offset
Date: Thu, 19 Mar 2020 09:16:43 +0100	[thread overview]
Message-ID: <CAK8P3a18YySozk6P77JpS58Hbtz=QQmLKw+PrzXbdOwtOQQuJA@mail.gmail.com> (raw)
In-Reply-To: <20200319081137.GC223854@dcbz.redhat.com>

On Thu, Mar 19, 2020 at 9:11 AM Adrian Reber <areber@redhat.com> wrote:

> With Arnd's idea of only using nanoseconds, timens_offset would then
> contain something like this:
>
> struct timens_offset {
>         __aligned_s64 monotonic_offset_ns;
>         __aligned_s64 boottime_offset_ns;
> };
>
> I kind of prefer adding boottime and monotonic directly to struct clone_args
>
>         __aligned_u64 tls;
>         __aligned_u64 set_tid;
>         __aligned_u64 set_tid_size;
> +       __aligned_s64 monotonic_offset_ns;
> +       __aligned_s64 boottime_offset_ns;
>  };

I would also prefer the second approach using two 64-bit integers
instead of a pointer, as it keeps the interface simpler to implement
and simpler to interpret by other tools.

      Arnd