linux-kernel - Re: [PATCH 4/4] net: Implement the per network namespace sysctl infrastructure

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Message-ID: <m13aun9zfe.fsf@ebiederm.dsl.xmission.com>
Date:	Fri, 30 Nov 2007 14:49:25 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Cedric Le Goater <clg@...ibm.com>,
	Linux Containers <containers@...ts.osdl.org>,
	Pavel Emelyanov <xemul@...nvz.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH 4/4] net: Implement the per network namespace sysctl infrastructure

"Serge E. Hallyn" <serue@...ibm.com> writes:

>
> Hey Eric,
>
> the patches look nice.
>
> The hand-forcing of the passed-in net_ns into a copy of current->nsproxy
> does make it seem like nsproxy may not be the best choice of what to
> pass in.  Doesn't only net_sysctl_root->lookup() look at the argument?

Yes.  Although I call it from __register_sysctl_paths.

> But I assume you don't want to be more general than sending in a
> nsproxy so as to dissuade abuse of this interface for needlessly complex
> sysctl interfaces?

A bit of that.  I would love to pass in a task_struct so you can use
anything from a task.  The trouble is I don't have any task_structs or
nsproxys with the proper value at the point where I am first setting
this up.  Further I have to have the full sysctl lookup working or I
could not call sysctl_check.

> (Well I expect that'll become clear once the the patches using this
> come out.)
>
> Are you planning to use this infrastructure for the uts and ipc
> sysctls as well?

Yes.  Where it comes in especially useful, is I can move /proc/sys
to /proc/sys/<tgid>/task/<pid>/sys.  And get a particular processes
view of sysctl.  

We also get a little more reuse of common functions.

Otherwise Pavel does have a point that using this for uts and ipc
is not a savings lines of code wise.

After having seen Pavel changes I am asking myself if there is a sane
way to remove the ctl_name argument from the ctl_path.

Anyway where I am with the nsproxy question was that I don't
see anything easily better.  What I have works and gets the job
done, and doesn't have any module unload races or holes where a sloppy
programmer can mess up the sysctl tree.  We needed a solution.
Trying any harder to find something better would take ages.  So
I figured this implementation was good enough.

Eric
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