From: Andrei Vagin <avagin@gmail.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
viro@zeniv.linux.org.uk, adobriyan@gmail.com,
davem@davemloft.net, akpm@linux-foundation.org,
christian.brauner@ubuntu.com, areber@redhat.com,
serge@hallyn.com, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Subject: Re: [PATCH 00/23] proc: Introduce /proc/namespaces/ directory to expose namespaces lineary
Date: Thu, 6 Aug 2020 01:05:40 -0700 [thread overview]
Message-ID: <20200806080540.GA18865@gmail.com> (raw)
In-Reply-To: <9ceb5049-6aea-1429-e35f-d86480f10d72@virtuozzo.com>
On Mon, Aug 03, 2020 at 01:03:17PM +0300, Kirill Tkhai wrote:
> On 31.07.2020 01:13, Eric W. Biederman wrote:
> > Kirill Tkhai <ktkhai@virtuozzo.com> writes:
> >
> >> On 30.07.2020 17:34, Eric W. Biederman wrote:
> >>> Kirill Tkhai <ktkhai@virtuozzo.com> writes:
> >>>
> >>>> Currently, there is no a way to list or iterate all or subset of namespaces
> >>>> in the system. Some namespaces are exposed in /proc/[pid]/ns/ directories,
> >>>> but some also may be as open files, which are not attached to a process.
> >>>> When a namespace open fd is sent over unix socket and then closed, it is
> >>>> impossible to know whether the namespace exists or not.
> >>>>
> >>>> Also, even if namespace is exposed as attached to a process or as open file,
> >>>> iteration over /proc/*/ns/* or /proc/*/fd/* namespaces is not fast, because
> >>>> this multiplies at tasks and fds number.
> >>>
> >>> I am very dubious about this.
> >>>
> >>> I have been avoiding exactly this kind of interface because it can
> >>> create rather fundamental problems with checkpoint restart.
> >>
> >> restart/restore :)
> >>
> >>> You do have some filtering and the filtering is not based on current.
> >>> Which is good.
> >>>
> >>> A view that is relative to a user namespace might be ok. It almost
> >>> certainly does better as it's own little filesystem than as an extension
> >>> to proc though.
> >>>
> >>> The big thing we want to ensure is that if you migrate you can restore
> >>> everything. I don't see how you will be able to restore these files
> >>> after migration. Anything like this without having a complete
> >>> checkpoint/restore story is a non-starter.
> >>
> >> There is no difference between files in /proc/namespaces/ directory and /proc/[pid]/ns/.
> >>
> >> CRIU can restore open files in /proc/[pid]/ns, the same will be with /proc/namespaces/ files.
> >> As a person who worked deeply for pid_ns and user_ns support in CRIU, I don't see any
> >> problem here.
> >
> > An obvious diffference is that you are adding the inode to the inode to
> > the file name. Which means that now you really do have to preserve the
> > inode numbers during process migration.
> >
> > Which means now we have to do all of the work to make inode number
> > restoration possible. Which means now we need to have multiple
> > instances of nsfs so that we can restore inode numbers.
> >
> > I think this is still possible but we have been delaying figuring out
> > how to restore inode numbers long enough that may be actual technical
> > problems making it happen.
>
> Yeah, this matters. But it looks like here is not a dead end. We just need
> change the names the namespaces are exported to particular fs and to support
> rename().
>
> Before introduction a principally new filesystem type for this, can't
> this be solved in current /proc?
do you mean to introduce names for namespaces which users will be able
to change? By default, this can be uuid.
And I have a suggestion about the structure of /proc/namespaces/.
Each namespace is owned by one of user namespaces. Maybe it makes sense
to group namespaces by their user-namespaces?
/proc/namespaces/
user
mnt-X
mnt-Y
pid-X
uts-Z
user-X/
user
mnt-A
mnt-B
user-C
user-C/
user
user-Y/
user
Do we try to invent cgroupfs for namespaces?
Thanks,
Andrei
next prev parent reply other threads:[~2020-08-06 11:05 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 11:59 [PATCH 00/23] proc: Introduce /proc/namespaces/ directory to expose namespaces lineary Kirill Tkhai
2020-07-30 11:59 ` [PATCH 01/23] ns: Add common refcount into ns_common add use it as counter for net_ns Kirill Tkhai
2020-07-30 13:35 ` Christian Brauner
2020-07-30 14:07 ` Kirill Tkhai
2020-07-30 15:59 ` Christian Brauner
2020-07-30 14:30 ` Christian Brauner
2020-07-30 14:34 ` Kirill Tkhai
2020-07-30 14:39 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 02/23] uts: Use generic ns_common::count Kirill Tkhai
2020-07-30 14:30 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 03/23] ipc: " Kirill Tkhai
2020-07-30 14:32 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 04/23] pid: " Kirill Tkhai
2020-07-30 14:37 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 05/23] user: " Kirill Tkhai
2020-07-30 14:46 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 06/23] mnt: " Kirill Tkhai
2020-07-30 14:49 ` Christian Brauner
2020-07-30 11:59 ` [PATCH 07/23] cgroup: " Kirill Tkhai
2020-07-30 14:50 ` Christian Brauner
2020-07-30 12:00 ` [PATCH 08/23] time: " Kirill Tkhai
2020-07-30 14:52 ` Christian Brauner
2020-07-30 12:00 ` [PATCH 09/23] ns: Introduce ns_idr to be able to iterate all allocated namespaces in the system Kirill Tkhai
2020-07-30 12:23 ` Matthew Wilcox
2020-07-30 13:32 ` Kirill Tkhai
2020-07-30 13:56 ` Matthew Wilcox
2020-07-30 14:12 ` Kirill Tkhai
2020-07-30 14:15 ` Matthew Wilcox
2020-07-30 14:20 ` Kirill Tkhai
2020-07-30 12:00 ` [PATCH 10/23] fs: Rename fs/proc/namespaces.c into fs/proc/task_namespaces.c Kirill Tkhai
2020-07-30 12:00 ` [PATCH 11/23] fs: Add /proc/namespaces/ directory Kirill Tkhai
2020-07-30 12:18 ` Alexey Dobriyan
2020-07-30 13:22 ` Kirill Tkhai
2020-07-30 13:26 ` Christian Brauner
2020-07-30 14:30 ` Kirill Tkhai
2020-07-30 20:47 ` kernel test robot
2020-07-30 22:20 ` kernel test robot
2020-08-05 8:17 ` kernel test robot
2020-08-05 8:17 ` [RFC PATCH] fs: namespaces_dentry_operations can be static kernel test robot
2020-07-30 12:00 ` [PATCH 12/23] user: Free user_ns one RCU grace period after final counter put Kirill Tkhai
2020-07-30 12:00 ` [PATCH 13/23] user: Add user namespaces into ns_idr Kirill Tkhai
2020-07-30 12:00 ` [PATCH 14/23] net: Add net " Kirill Tkhai
2020-07-30 12:00 ` [PATCH 15/23] pid: Eextract child_reaper check from pidns_for_children_get() Kirill Tkhai
2020-07-30 12:00 ` [PATCH 16/23] proc_ns_operations: Add can_get method Kirill Tkhai
2020-07-30 12:00 ` [PATCH 17/23] pid: Add pid namespaces into ns_idr Kirill Tkhai
2020-07-30 12:00 ` [PATCH 18/23] uts: Free uts namespace one RCU grace period after final counter put Kirill Tkhai
2020-07-30 12:01 ` [PATCH 19/23] uts: Add uts namespaces into ns_idr Kirill Tkhai
2020-07-30 12:01 ` [PATCH 20/23] ipc: Add ipc " Kirill Tkhai
2020-07-30 12:01 ` [PATCH 21/23] mnt: Add mount " Kirill Tkhai
2020-07-30 12:01 ` [PATCH 22/23] cgroup: Add cgroup " Kirill Tkhai
2020-07-30 12:01 ` [PATCH 23/23] time: Add time " Kirill Tkhai
2020-07-30 13:08 ` [PATCH 00/23] proc: Introduce /proc/namespaces/ directory to expose namespaces lineary Christian Brauner
2020-07-30 13:38 ` Christian Brauner
2020-07-30 14:34 ` Eric W. Biederman
2020-07-30 14:42 ` Christian Brauner
2020-07-30 15:01 ` Kirill Tkhai
2020-07-30 22:13 ` Eric W. Biederman
2020-07-31 8:48 ` Pavel Tikhomirov
2020-08-03 10:03 ` Kirill Tkhai
2020-08-03 10:51 ` Alexey Dobriyan
2020-08-06 8:05 ` Andrei Vagin [this message]
2020-08-07 8:47 ` Kirill Tkhai
2020-08-10 17:34 ` Andrei Vagin
2020-08-11 10:23 ` Kirill Tkhai
2020-08-12 17:53 ` Andrei Vagin
2020-08-13 8:12 ` Kirill Tkhai
2020-08-14 1:16 ` Andrei Vagin
2020-08-14 15:11 ` Kirill Tkhai
2020-08-14 19:21 ` Andrei Vagin
2020-08-17 14:05 ` Kirill Tkhai
2020-08-17 15:48 ` Eric W. Biederman
2020-08-17 17:47 ` Christian Brauner
2020-08-17 18:53 ` Eric W. Biederman
2020-08-04 5:43 ` Andrei Vagin
2020-08-04 12:11 ` Pavel Tikhomirov
2020-08-04 14:47 ` Kirill Tkhai
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