linux-kernel - Re: [PATCH 04/11] cxl/core: Clamp max lock

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Date:   Wed, 9 Mar 2022 11:59:13 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Rafael J Wysocki <rafael.j.wysocki@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-cxl@...r.kernel.org, Linux NVDIMM <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH 04/11] cxl/core: Clamp max lock_class

On Wed, Mar 9, 2022 at 10:27 AM Jonathan Cameron
<Jonathan.Cameron@...wei.com> wrote:
>
> On Mon, 28 Feb 2022 18:49:11 -0800
> Dan Williams <dan.j.williams@...el.com> wrote:
>
> > MAX_LOCKDEP_SUBCLASSES limits the depth of the CXL topology that can be
> > validated by lockdep. Given that the cxl_test topology is already at
> > this limit collapse some of the levels and clamp the max depth.
> >
> > Cc: Alison Schofield <alison.schofield@...el.com>
> > Cc: Vishal Verma <vishal.l.verma@...el.com>
> > Cc: Ira Weiny <ira.weiny@...el.com>
> > Cc: Ben Widawsky <ben.widawsky@...el.com>
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > ---
> >  drivers/cxl/cxl.h |   21 +++++++++++++++++----
> >  1 file changed, 17 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index 97e6ca7e4940..1357a245037d 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -501,20 +501,33 @@ enum cxl_lock_class {
> >       CXL_ANON_LOCK,
> >       CXL_NVDIMM_LOCK,
> >       CXL_NVDIMM_BRIDGE_LOCK,
>
> I'd be tempted to give explicit value to the one above as well
> so it's immediate clear there is deliberate duplication here.

Sounds good.

I also notice that clamp_lock_class() should return -1 when it wants
to disable validation, not zero.