| Message ID | 0825f166-6f20-59a9-45a9-5ffe9009150e@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Mar 31, 2017 at 2:45 AM, Kirill Tkhai <ktkhai@virtuozzo.com> wrote: > On 31.03.2017 04:04, Andrei Vagin wrote: >> On Thu, Mar 30, 2017 at 03:05:20PM -0700, Andrew Morton wrote: >>> On Thu, 30 Mar 2017 13:27:59 +0300 Kirill Tkhai <ktkhai@virtuozzo.com> wrote: >>> >>>> pid_ns_for_children set by a task is known only to the task itself, >>>> and it's impossible to identify it from outside. >>>> >>>> It's a big problem for checkpoint/restore software like CRIU, >>>> because it can't correctly handle tasks, that do setns(CLONE_NEWPID) >>>> in proccess of their work. >>>> >>>> This patch solves the problem, and it exposes pid_ns_for_children >>>> to ns directory in standard way with the name "pid_for_children": >>>> >>>> ~# ls /proc/5531/ns -l | grep pid >>>> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] >>>> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] >>>> >>>> --- a/fs/proc/namespaces.c >>>> +++ b/fs/proc/namespaces.c >>>> @@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { >>>> #endif >>>> #ifdef CONFIG_PID_NS >>>> &pidns_operations, >>>> + &pidns_for_children_operations, >>>> #endif >>> >>> This interface should be documented somewhere under Documentation/. >>> But I can't immediately find where the /proc/pid/ns/ pseudo-files are >>> documented... >> >> I know that they are documented in man7/namespaces.7 >> >> https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man7/namespaces.7#n187 > > I suggest the below patch, but it's too early for the man description till > the feature is in mainline, because the man page requires commit id of the feature. > > [PATCH] namespaces.7: Document the /proc/[pid]/ns/pid_for_children file > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > man7/namespaces.7 | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > diff --git a/man7/namespaces.7 b/man7/namespaces.7 > index 6dfceaa2a..06041774f 100644 > --- a/man7/namespaces.7 > +++ b/man7/namespaces.7 > @@ -125,6 +125,7 @@ lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 ipc \-> ipc:[4026531839] > lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 mnt \-> mnt:[4026531840] > lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 net \-> net:[4026531969] > lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid \-> pid:[4026531836] > +lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid_for_children -> pid:[4026531834] Minor nit: this needs to be "\-" for the "-" > lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 user \-> user:[4026531837] > lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 uts \-> uts:[4026531838] > .fi > @@ -186,7 +187,14 @@ This file is a handle for the network namespace of the process. > .TP > .IR /proc/[pid]/ns/pid " (since Linux 3.8)" > .\" commit 57e8391d327609cbf12d843259c968b9e5c1838f > -This file is a handle for the PID namespace of the process. > +This file is a handle for the PID namespace of the process. It's > +permanent during the whole process life. > +.TP > +.IR /proc/[pid]/ns/pid_for_children " (since Linux 4.12)" > +.\" commit FIXME > +This file is a handle for the PID namespace of a next born child > +of the process. It's changed after unshare(2) and via setns(2), > +so the file may differ from /proc/[pid]/ns/pid. > .TP > .IR /proc/[pid]/ns/user " (since Linux 3.8)" > .\" commit cde1975bc242f3e1072bde623ef378e547b73f91 > -Kees
diff --git a/man7/namespaces.7 b/man7/namespaces.7 index 6dfceaa2a..06041774f 100644 --- a/man7/namespaces.7 +++ b/man7/namespaces.7 @@ -125,6 +125,7 @@ lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 ipc \-> ipc:[4026531839] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 mnt \-> mnt:[4026531840] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 net \-> net:[4026531969] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid \-> pid:[4026531836] +lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid_for_children -> pid:[4026531834] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 user \-> user:[4026531837] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 uts \-> uts:[4026531838] .fi @@ -186,7 +187,14 @@ This file is a handle for the network namespace of the process. .TP .IR /proc/[pid]/ns/pid " (since Linux 3.8)" .\" commit 57e8391d327609cbf12d843259c968b9e5c1838f -This file is a handle for the PID namespace of the process. +This file is a handle for the PID namespace of the process. It's +permanent during the whole process life. +.TP +.IR /proc/[pid]/ns/pid_for_children " (since Linux 4.12)" +.\" commit FIXME +This file is a handle for the PID namespace of a next born child +of the process. It's changed after unshare(2) and via setns(2), +so the file may differ from /proc/[pid]/ns/pid. .TP .IR /proc/[pid]/ns/user " (since Linux 3.8)" .\" commit cde1975bc242f3e1072bde623ef378e547b73f91