Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1449562
| From | ebiederm@xmission.com (Eric W. Biederman) |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces |
| Date | 2016-07-25 17:20 +0200 |
| Message-ID | <rYPPH-6aR-13@gated-at.bofh.it> (permalink) |
| References | (3 earlier) <rXNmW-WX-23@gated-at.bofh.it> <rXNmW-WX-19@gated-at.bofh.it> <rYMyt-43Y-1@gated-at.bofh.it> <rYOgW-584-31@gated-at.bofh.it> <rYPmF-5Ly-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes:
> Hi Eric,
>
> On 07/25/2016 03:18 PM, Eric W. Biederman wrote:
>> "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes:
>>
>>> Hi Andrey,
>>>
>>> On 07/22/2016 08:25 PM, Andrey Vagin wrote:
>>>> On Thu, Jul 21, 2016 at 11:48 PM, Michael Kerrisk (man-pages)
>>>> <mtk.manpages@gmail.com> wrote:
>>>>> Hi Andrey,
>>>>>
>>>>>
>>>>> On 07/21/2016 11:06 PM, Andrew Vagin wrote:
>>>>>>
[snip]
>>>>>> where ioctl_type is one of the following:
>>>>>>
>>>>>> NS_GET_USERNS
>>>>>> Returns a file descriptor that refers to an owning user names‐
>>>>>> pace.
>>>>>>
>>>>>> NS_GET_PARENT
>>>>>> Returns a file descriptor that refers to a parent namespace.
>>>>>> This ioctl(2) can be used for pid and user namespaces. For user
>>>>>> namespaces, NS_GET_PARENT and NS_GET_USERNS have the same mean‐
>>>>>> ing.
>>>
>>> For each of the above, I think it is worth mentioning that the
>>> close-on-exec flag is set for the returned file descriptor.
>>
>> Hmm. That is an odd default.
>
> Why do you say that? It's pretty common as the default for various
> APIs that create new FDs these days. (There's of course a strong argument
> that the original UNIX default was a design blunder...)
Interesting. I haven't kept up on that, but it seems reasonable.
[snip]
>>> So, from my point of view, the important piece that was missing from
>>> your commit message was the note to use readlink("/proc/self/fd/%d")
>>> on the returned FDs. I think that detail needs to be part of the
>>> commit message (and also the man page text). I think it even be
>>> helpful to include the above program as part of the commit message:
>>> it helps people more quickly grasp the API.
>>
>> Please, please make the standard way to compare these things fstat.
>> That is much less magic than a symlink, and a little more future proof.
>> Possibly even kcmp.
>
> As in fstat() to get the st_ino field, right?
Both the st_ino and st_dev fields.
The most likely change to support checkpoint/restart in the future is to
preserve st_ino across migrations and instantiate a different instance
of nsfs to hold the inode numbers from the previous machine.
We would need to handle the preservation carefully or else there is
a chance that two namespace file descriptors (collected from different
sources) with different st_dev and st_ino fields may actuall refer to
the same object.
Which is a long way of saying we have the st_dev field please use it,
it may matter at some point.
Eric
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 0/5 RFC] Add an interface to discover relationships between namespaces Andrey Vagin <avagin@openvz.org> - 2016-07-14 20:30 +0200
[PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace Andrey Vagin <avagin@openvz.org> - 2016-07-14 20:30 +0200
Re: [PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace "W. Trevor King" <wking@tremily.us> - 2016-07-14 21:10 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces Andrey Vagin <avagin@openvz.org> - 2016-07-15 00:10 +0200
[PATCH 5/5] tools/testing: add a test to check nsfs ioctl-s Andrey Vagin <avagin@openvz.org> - 2016-07-15 04:20 +0200
[PATCH 4/5] nsfs: add ioctl to get a parent namespace Andrey Vagin <avagin@openvz.org> - 2016-07-15 04:20 +0200
Re: [PATCH 4/5] nsfs: add ioctl to get a parent namespace ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 07:30 +0200
[PATCH 3/5] nsfs: add ioctl to get an owning user namespace for ns file descriptor Andrey Vagin <avagin@openvz.org> - 2016-07-15 04:20 +0200
[PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace Andrey Vagin <avagin@openvz.org> - 2016-07-15 04:20 +0200
Re: [PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 07:20 +0200
Re: [PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 16:50 +0200
Re: [PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace "W. Trevor King" <wking@tremily.us> - 2016-07-24 19:10 +0200
Re: [PATCH 2/5] kernel: add a helper to get an owning user namespace for a namespace "W. Trevor King" <wking@tremily.us> - 2016-07-24 19:00 +0200
Re: [PATCH 1/5] namespaces: move user_ns into ns_common ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 07:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 07:30 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-21 16:50 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces Andrey Vagin <avagin@openvz.org> - 2016-07-22 20:30 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-25 13:50 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-25 15:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-25 16:50 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Serge E. Hallyn" <serge@hallyn.com> - 2016-07-25 17:00 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-25 17:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-25 17:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-26 10:10 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "W. Trevor King" <wking@tremily.us> - 2016-07-26 20:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-26 21:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-28 12:50 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-28 15:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-28 21:10 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-29 20:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-07-31 23:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-26 22:00 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "W. Trevor King" <wking@tremily.us> - 2016-07-23 23:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces James Bottomley <James.Bottomley@HansenPartnership.com> - 2016-07-23 23:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "W. Trevor King" <wking@tremily.us> - 2016-07-24 00:10 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 00:20 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces "W. Trevor King" <wking@tremily.us> - 2016-07-24 00:40 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces ebiederm@xmission.com (Eric W. Biederman) - 2016-07-24 07:10 +0200
Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces Alban Crequy <alban.crequy@gmail.com> - 2016-08-01 21:20 +0200
csiph-web