linux-kernel - Re: [RFC 1/8] mm: add overflow and underflow checks for page->

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Message-ID: <YXjByyquuaN3ZKRq@casper.infradead.org>
Date:   Wed, 27 Oct 2021 04:04:43 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        linux-m68k@...ts.linux-m68k.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        william.kucharski@...cle.com,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        schmitzmic@...il.com, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>,
        Muchun Song <songmuchun@...edance.com>, weixugc@...gle.com,
        Greg Thelen <gthelen@...gle.com>
Subject: Re: [RFC 1/8] mm: add overflow and underflow checks for
 page->_refcount

On Tue, Oct 26, 2021 at 09:21:29PM -0400, Pasha Tatashin wrote:
> I think we can do that by using:
> atomic_fetch_*() and check for overflow/underflow after operation. I
> will send the updated series soon.

Please include performance measurements.  You're adding code to some hot
paths.