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Date:   Wed, 27 Oct 2021 04:04:43 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Pasha Tatashin <pasha.tatashin@soleen.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        linux-m68k@lists.linux-m68k.org,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        william.kucharski@oracle.com,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        schmitzmic@gmail.com, Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>,
        Muchun Song <songmuchun@bytedance.com>, weixugc@google.com,
        Greg Thelen <gthelen@google.com>
Subject: Re: [RFC 1/8] mm: add overflow and underflow checks for
 page->_refcount
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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.