linux-kernel - Re: [PATCH] rss_stat: Add support to detect RSS updates of external mm

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Message-ID: <20191108084707.fwy6junacy4b4fld@pathway.suse.cz>
Date:   Fri, 8 Nov 2019 09:47:07 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, Ioannis Ilkos <ilkos@...gle.com>,
        minchan@...gle.com, primiano@...gle.com, fmayer@...gle.com,
        hjd@...gle.com, joaodias@...gle.com, lalitm@...gle.com,
        rslawik@...gle.com, sspatil@...gle.com, timmurray@...gle.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Changbin Du <changbin.du@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Joe Perches <joe@...ches.com>,
        Kees Cook <keescook@...omium.org>, linux-mm@...ck.org,
        Michal Hocko <mhocko@...e.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] rss_stat: Add support to detect RSS updates of external
 mm

On Thu 2019-11-07 13:07:51, Joel Fernandes wrote:
> On Wed, Nov 06, 2019 at 09:59:59AM +0100, Petr Mladek wrote:
> > On Tue 2019-11-05 21:44:51, Joel Fernandes (Google) wrote:
> > > Also vsprintf.c is refactored a bit to allow reuse of hashing code.
> > 
> > I agree with Sergey that it would make sense to move this outside
> > vsprintf.c.
> 
> I am of the opinion that its Ok to have it this way and I am not sure if
> another translation unit is worth it just for this. If we have more users,
> then yes we can consider splitting into its own translation unit at that
> time.

Fair enough. I still think that it would make sense to move the code
but I do not want to block this patch because of this.

My view is that vsprintf.c is huge and the hashing-related code
is lost there. It consists of more pieces, early_param, static key,
workqueue work.

> If Andrew Morton objects, then I'll do it since the intention was for this
> patch to go through his tree and I believe he is Ok with it this way.
> 
> > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > > index dee8fc467fcf..401baaac1813 100644
> > > --- a/lib/vsprintf.c
> > > +++ b/lib/vsprintf.c
> > > @@ -761,11 +761,34 @@ static int __init initialize_ptr_random(void)
> > >  early_initcall(initialize_ptr_random);
> > >  
> > >  /* Maps a pointer to a 32 bit unique identifier. */
> > > +int ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
> > > +{
> > > +	const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
> > 
> > str is unused.
> 
> I believe Andrew has already fixed this in his tree.
> 
> linux-next has local variable removed now:
> 7422993b4f8e ("rss_stat-add-support-to-detect-rss-updates-of-external-mm-fix")

I see. With this fix, feel free to add:

Acked-by: Petr Mladek <pmladek@...e.com> # lib/vsprintf.c

The clean up could be done by a followup patches.

Best Regards,
Petr