Re: [PATCH v4 7/7] net: register debugfs file for net_device refcnt tracker

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2025-04-23 at 16:53 -0700, Jakub Kicinski wrote:
> On Fri, 18 Apr 2025 10:24:31 -0400 Jeff Layton wrote:
> > +	/* Register debugfs file for the refcount tracker */
> > +	if (snprintf(name, sizeof(name), "netdev-%s@%p", dev->name, dev) < sizeof(name))
> > +		ref_tracker_dir_debugfs(&dev->refcnt_tracker, name);
> 
> Names are not unique and IIUC debugfs is not namespaced.
> How much naming the objects in a "user readable" fashion actually
> matter? It'd be less churn to create some kind of "object class"
> with a directory level named after what's already passed to
> ref_tracker_dir_init() and then id the objects by the pointer value 
> as sub-dirs of that?

That sounds closer to what I had done originally. Andrew L. suggested
the flat directory that this version represents. I'm fine with whatever
hierarchy, but let's decide that before I respin again.

When I was tracking down net namespace leaks recently, it was very nice
to have the inode number of the leaked netns's in the filenames. I
would have probably had to grovel around with drgn to figure out the
address if that weren't embedded in the name. I think we probably ought
to leave it up to each subsystem how it names its files. The
discriminators between different types of objects can vary wildly.

One thing that might be simpler is to make ref_tracker_dir_debugfs() a
varargs function and allow passing in a format string and set of
arguments for it. That might make things simpler for the callers.
-- 
Jeff Layton <jlayton@kernel.org>