Re: [PATCH v13 0/9] ref_tracker: add ability to register a debugfs file for a ref_tracker_dir

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2025-06-03 at 19:29 -0700, Jakub Kicinski wrote:
> On Tue, 03 Jun 2025 07:27:11 -0400 Jeff Layton wrote:
> > For those just joining in, this series adds a new top-level
> > "ref_tracker" debugfs directory, and has each ref_tracker_dir register a
> > file in there as part of its initialization. It also adds the ability to
> > register a symlink with a more human-usable name that points to the
> > file, and does some general cleanup of how the ref_tracker object names
> > are handled.
> > 
> > This reposting is mostly to address Krzysztof's comments. I've dropped
> > the i915 patch, and rebased the rest of the series on top.
> > 
> > Note that I still see debugfs: warnings in the i915 driver even when we
> > gate the registration of the debugfs file on the classname pointer being
> > NULL. Here is a CI report from v12:
> > 
> >     https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_148490v8/bat-arls-6/igt@i915_selftest@live@workarounds.html
> > 
> > I think the i915 driver is doing something it shouldn't with these
> > objects. They seem to be initialized more than once, which could lead
> > to leaked ref_tracker objects. It would be good for one of the i915
> > maintainers to comment on whether this is a real problem.
> 
> I still see the fs crashes:
> https://netdev-3.bots.linux.dev/vmksft-packetdrill-dbg/results/149560/2-tcp-slow-start-slow-start-app-limited-pkt/stderr
> I'll hide this series from patchwork for now. We will pull from Linus
> on Thu, I'll reactivate it and let's see if the problem was already
> fixed.

Sorry, I never got any mail about those failures. I would have looked
at that sooner. It looks like the last netns reference can be put in a
rcu callback? That makes sense.

I think ref_tracker_dir_exit() has to remain safe to call from any
context. Perhaps we can defer the dentry deletion to the system_wq?

We can drop this series for now. I'll have to think about this.

Thanks,
-- 
Jeff Layton <jlayton@kernel.org>