Messages in this thread | | | Date | Mon, 16 Oct 2017 18:24:36 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v4] pidns: introduce syscall translate_pid |
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On 10/13, Konstantin Khlebnikov wrote: > > > On 13.10.2017 19:05, Oleg Nesterov wrote: > > > >I won't insist, but this suggests we should add a new helper, > >get_ns_by_fd_type(fd, type), and convert get_net_ns_by_fd() to use it > >as well. > > That was in v3. > > I'll prefer to this later, separately. And replace fget with fdget which > allows to do this without atomic operations if task is single-threaded.
OK, agreed,
> >Stupid question. Can't we make a simpler API which doesn't need /proc/ ? > >I mean, > > > > sys_translate_pid(pid_t pid, pid_t source_pid, pid_t target_pid) > > { > > struct pid_namespace *source_ns, *target_ns; > > > > source_ns = task_active_pid_ns(find_task_by_vpid(source_pid)); > > target_ns = task_active_pid_ns(find_task_by_vpid(target_pid)); > > > > ... > > } > > > Yes, this is more limited... Do you have a use-case when this is not enough? > > That was in v1 but considered too racy.
Hmm, I don't understand...
Yes sure, this is racy but open("/proc/$pid/ns/pid") is racy too?
OK, once you do fd=open("/proc/$pid/ns/pid") you can use this fd even after its owner exits, while find_task_by_vpid() will fail or find another task if this pid was already reused.
But once again, do you have a use-case when this is important?
> But we could merge both ways: > > source >= 0 - pidns fs > source < 0 - task_pid = -source
But for what? I must have missed something...
Oleg.
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