Re: [PATCH v6 08/10] net: add symlinks to ref_tracker_dir for netns

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2025-04-30 at 14:29 -0700, Kuniyuki Iwashima wrote:
> From: Jeff Layton <jlayton@kernel.org>
> Date: Wed, 30 Apr 2025 08:06:54 -0700
> > After assigning the inode number to the namespace, use it to create a
> > unique name for each netns refcount tracker with the ns.inum value in
> > it, and register a symlink to the debugfs file for it.
> > 
> > init_net is registered before the ref_tracker dir is created, so add a
> > late_initcall() to register its files and symlinks.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  net/core/net_namespace.c | 28 +++++++++++++++++++++++++++-
> >  1 file changed, 27 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> > index 008de9675ea98fa8c18628b2f1c3aee7f3ebc9c6..6cbc8eabb8e56c847fc34fa8ec9994e8b275b0af 100644
> > --- a/net/core/net_namespace.c
> > +++ b/net/core/net_namespace.c
> > @@ -763,12 +763,38 @@ struct net *get_net_ns_by_pid(pid_t pid)
> >  }
> >  EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
> >  
> > +#ifdef CONFIG_NET_NS_REFCNT_TRACKER
> > +static void net_ns_net_debugfs(struct net *net)
> > +{
> > +	ref_tracker_dir_symlink(&net->refcnt_tracker, "netns-%u-refcnt", net->ns.inum);
> > +	ref_tracker_dir_symlink(&net->notrefcnt_tracker, "netns-%u-notrefcnt", net->ns.inum);
> 
> Could you use net->net_cookie ?
> 
> net->ns.inum is always 1 when CONFIG_PROC_FS=n.

My main use-case for this is to be able to match the inode number in
the /proc/<pid>/ns/net symlink with the correct ref_tracker debugfs
file. Is there a way to use the net_cookie to make that association?

If there isn't, and ns.inum is always 1 with procfs is disabled, we
could just skip adding the symlink when CONFIG_PROC_FS=n.
-- 
Jeff Layton <jlayton@kernel.org>