From: Adrian Reber <areber@redhat.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Andrei Vagin <avagin@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
Eric Biederman <ebiederm@xmission.com>,
Pavel Emelyanov <ovzxemul@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
Dmitry Safonov <0x7f454c46@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: Tue, 24 Mar 2020 17:25:46 +0100 [thread overview]
Message-ID: <20200324162546.GG358599@dcbz.redhat.com> (raw)
In-Reply-To: <20200324160945.orcm75avj2ol3eop@wittgenstein>
On Tue, Mar 24, 2020 at 05:09:45PM +0100, Christian Brauner wrote:
> On Fri, Mar 20, 2020 at 11:33:55AM -0700, Andrei Vagin wrote:
> > On Thu, Mar 19, 2020 at 11:29:55AM +0100, Christian Brauner wrote:
> > > On Thu, Mar 19, 2020 at 09:16:43AM +0100, Arnd Bergmann wrote:
> > > > 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.
> > >
> > > Why I don't like has two reasons. There's the scenario where we have
> > > added new extensions after the new boottime member and then we introduce
> > > another offset. Then you'd be looking at:
> > >
> > > __aligned_u64 tls;
> > > __aligned_u64 set_tid;
> > > __aligned_u64 set_tid_size;
> > > + __aligned_s64 monotonic_offset_ns;
> > > + __aligned_s64 boottime_offset_ns;
> > > __aligned_s64 something_1
> > > __aligned_s64 anything_2
> > > + __aligned_s64 sometime_offset_ns
> > >
> > > which bothers me just by looking at it. That's in addition to adding two
> > > new members to the struct when most people will never set CLONE_NEWTIME.
> > > We'll also likely have more features in the future that will want to
> > > pass down more info than we want to directly expose in struct
> > > clone_args, e.g. for a long time I have been thinking about adding a
> > > struct for CLONE_NEWUSER that allows you to specify the id mappings you
> > > want the new user namespace to get. We surely don't want to force all
> > > new info into the uppermost struct. So I'm not convinced we should here.
> >
> > I think here we can start thinking about a netlink-like interface.
>
> I think netlink is just not a great model for an API and I would not
> want us to go down that route.
>
> I kept thinking about this for a bit and I think that we will end up
> growing more namespace-related functionality. So one thing that came to
> my mind is the following layout:
>
> struct {
> struct {
> __s64 monotonic;
> __s64 boot;
> } time;
> } namespaces;
>
> struct _clone_args {
> __aligned_u64 flags;
> __aligned_u64 pidfd;
> __aligned_u64 child_tid;
> __aligned_u64 parent_tid;
> __aligned_u64 exit_signal;
> __aligned_u64 stack;
> __aligned_u64 stack_size;
> __aligned_u64 tls;
> __aligned_u64 set_tid;
> __aligned_u64 set_tid_size;
> __aligned_u64 namespaces;
> __aligned_u64 namespaces_size;
> };
>
> Then when we end up adding id mapping support for CLONE_NEWUSER we can
> extend this with:
>
> struct {
> struct {
> __aligned_u64 monotonic;
> __aligned_u64 boot;
> } time;
>
> struct {
> /* id mapping members */
> } user;
> } namespaces;
>
> Thoughts? Other ideas?
Works for me.
If we add the user namespace id mappings and then at some point a third
element for the time namespace appears it would also start to be mixed.
Just as you mentioned that a few mails ago.
> > > __aligned_u64 set_tid_size;
> > > + __aligned_s64 monotonic_offset_ns;
> > > + __aligned_s64 boottime_offset_ns;
> > > __aligned_s64 something_1
> > > __aligned_s64 anything_2
> > > + __aligned_s64 sometime_offset_ns
If we can live with something like this in the namespaces struct you
proposed, it works for me.
Adrian
next prev parent reply other threads:[~2020-03-24 16:26 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 8:30 clone3: allow creation of time namespace with offset Adrian Reber
2020-03-17 8:30 ` [PATCH 1/4] ns: prepare time namespace for clone3() Adrian Reber
2020-03-18 10:57 ` Cyrill Gorcunov
2020-03-18 11:17 ` Christian Brauner
2020-03-18 11:28 ` Cyrill Gorcunov
2020-03-18 11:57 ` Christian Brauner
2020-03-18 11:58 ` Christian Brauner
2020-03-18 12:07 ` Cyrill Gorcunov
2020-03-17 8:30 ` [PATCH 2/4] clone3: allow creation of time namespace with offset Adrian Reber
2020-03-18 12:13 ` Christian Brauner
2020-03-17 8:30 ` [PATCH 3/4] clone3: align structs and comments Adrian Reber
2020-03-17 8:30 ` [PATCH 4/4] selftests: add clone3() in time namespace test Adrian Reber
2020-03-17 8:41 ` clone3: allow creation of time namespace with offset Christian Brauner
2020-03-17 8:43 ` Christian Brauner
2020-03-17 9:40 ` Michael Kerrisk (man-pages)
2020-03-17 14:23 ` Aleksa Sarai
2020-03-17 16:09 ` Christian Brauner
2020-03-18 10:18 ` Arnd Bergmann
2020-03-19 8:11 ` Adrian Reber
2020-03-19 8:16 ` Arnd Bergmann
2020-03-19 10:29 ` Christian Brauner
2020-03-20 18:33 ` Andrei Vagin
2020-03-24 16:09 ` Christian Brauner
2020-03-24 16:25 ` Adrian Reber [this message]
2020-03-24 17:56 ` Christian Brauner
2020-03-25 7:58 ` Adrian Reber
2020-03-25 11:26 ` Christian Brauner
2020-04-01 11:40 ` Michael Kerrisk (man-pages)
2020-04-01 11:46 ` Christian Brauner
2020-04-01 12:15 ` Michael Kerrisk (man-pages)
2020-05-29 12:26 ` Michael Kerrisk (man-pages)
2020-05-29 15:10 ` Adrian Reber
2020-05-29 15:13 ` Christian Brauner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200324162546.GG358599@dcbz.redhat.com \
--to=areber@redhat.com \
--cc=0x7f454c46@gmail.com \
--cc=arnd@arndb.de \
--cc=avagin@gmail.com \
--cc=christian.brauner@ubuntu.com \
--cc=cyphar@cyphar.com \
--cc=ebiederm@xmission.com \
--cc=gorcunov@openvz.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mtk.manpages@gmail.com \
--cc=oleg@redhat.com \
--cc=ovzxemul@gmail.com \
--cc=rppt@linux.ibm.com \
--cc=rstoyanov1@gmail.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).