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Sun, 19 Jul 2026 08:20:56 -0700 (PDT) Date: Sun, 19 Jul 2026 15:20:55 +0000 From: Pasha Tatashin To: tt roxy Cc: Andrew Morton , Ren Wei , linux-mm@kvack.org, pasha.tatashin@soleen.com, vega@nebusec.ai, Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner Subject: Re: [PATCH 1/1] mm/page_table_check: widen map counters Message-ID: References: <20260717221108.c6caf7dd11a47bd7c32aa6ff@linux-foundation.org> <20260717223112.ba8646377b103cae717580c8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5BB3FC0007 X-Stat-Signature: hrsb8k8yjadf8txtkcfyg78hobb1wm6j X-Rspam-User: X-HE-Tag: 1784474458-413406 X-HE-Meta: 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 ubA2t4Ld JHDbFUJ4mkg0WeC7c/Q0G55SBB22yAb+HKVTU9tOY7sWRVfxNTVFWwdP53Y/QcEKRH3O1FvWFE1RkBbz1Js5Pg+i8pY15SEwBAICSecHIPoj35eqlNU5XfmoBc8L/p+x0b10yZClz/DINdmPM+P3iUk69Ae+mOXxmkA+aM8HJyCiru6b7hxmKetfGcu9xrUh+VcxJH6lH3W6M+FeSTHJmBYNkGa7lgEsZgKkFASTToYq2BsE4kWJgTothzhofuzjFIK6qRYuxJhcjjPdmW7hXxRNZ/tSq74poULV+UlHncePvjAPbfD9tDXSIeLj/Vv1dnyqlYGd2N03uQHGWe0SgWXiDPLin23LPMP3I6+IjbS1AJ9mz8A/yhr6QnKS3HUihoBEgj0ksTLL7hB3XLcDnN7eUAPjhKbfO1QILFCfpMu4SCOYwOqqWHcApJanl0lvMdaJKCOi/oLIkigLzmx96JfTeRw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07-18 18:21, tt roxy wrote: > On Sat, Jul 18, 2026 at 1:31 PM Andrew Morton wrote: > > > > On Fri, 17 Jul 2026 22:11:08 -0700 Andrew Morton wrote: > > > > > Probably adding __aligned(sizeof(atomic64_t)) will address? > > > > err, no. I think page_ext code will need alteration for this. > > Thanks Andrew and Matthew. > > Agreed. Widening the counters is not the right direction: it changes the > page_ext storage/alignment requirements, and normal page mapcount is still > 32-bit as Matthew pointed out. Also, double page table check overhead. So, I agree let's address the special case instead of widening page_ext. Thanks, Pasha > > I'll rework this around a zero-page-specific fix and send v2 after checking > the exact page_table_check paths. > > Thanks for the review.