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From: Lance Yang Date: Tue, 30 Sep 2025 09:48:34 +0800 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWCEPx5gCS0R5WB1gxGkcM2qm8EcK_iKsr9vf6l6Pm-AjVLkn3oGjXPud8c Message-ID: Subject: Re: [PATCH 1/1] mm: prevent poison consumption when splitting THP To: "Zhuo, Qiuxu" , David Hildenbrand Cc: "Luck, Tony" , Jiaqi Yan , "akpm@linux-foundation.org" , "lorenzo.stoakes@oracle.com" , "linmiaohe@huawei.com" , "ziy@nvidia.com" , "baolin.wang@linux.alibaba.com" , "Liam.Howlett@oracle.com" , "npache@redhat.com" , "ryan.roberts@arm.com" , "dev.jain@arm.com" , "baohua@kernel.org" , "nao.horiguchi@gmail.com" , "Chen, Farrah" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Zaborowski Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 31CB3C000D X-Stat-Signature: ma88q3kagfwqqjd7bych88phstiozyms X-Rspam-User: X-HE-Tag: 1759196963-155124 X-HE-Meta: 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 9ZGS3oqS 0YEGvL8TRXtBSueyj0EWWIXusbiIW8l1865f1LxSWF/b457iOBUct6ANtgWkRDXREV+W/6WiTgop3Xrf6t8CDXgkaVhhjDlNPvE0Bq+D4jXGcBVuol/Uoyfg9cfEMjAfYo0GB/1uBosdv+9XHnugjdHBsy4o7rLsekWDZykjKSUFYHHL9tCTd0mHcqNrbw7jgDN1NZLwmnsIxWyROSde4urWbD0yoa1N1ZwEuR8lXw3UKCKla7X+U7vmQ58cOpoQo6bC0Ns5ItN83S+0gxzKorOrWk74AMiE+rc6hxHoAHfaqf0OGdPZMh4xsLLgq8pY95ZQzywuvf3R7qkE5yaDaN0grRulR+P50nyV3 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 30, 2025 at 3:07=E2=80=AFAM David Hildenbrand wrote: > > On 29.09.25 18:30, Zhuo, Qiuxu wrote: > > Hi Tony, > > > >> From: Luck, Tony > >> [...] > >> Subject: RE: [PATCH 1/1] mm: prevent poison consumption when splitting= THP > >> > >>> Miaohe mentioned in another e-mail that there was an HWPoisoned flag > >> for the raw error 4K page. > >>> We could use that flag just to skip that raw error page and still use > >>> the zeropage for other healthy sub-pages. I'll try that. > >> > >> That HWPoisoned flag is only set for raw pages where an error has been > >> detected. Maybe Linux could implement an > >> "is_this_page_all_zero_mc_safe()"[1] that would catch undetected poiso= n > > > > This sounds like a great suggestion to me. > > Let's see what others think about this and the name (though the name al= ready LGTM =F0=9F=98=8A). > > The function name is just ... special. Not the good type of special IMHO.= :) > > Note that we'll be moving to pages_identical() in [1]. Maybe we would > want a pages_identical_mc() or sth. like that as a follow up later. > > > So in any case, make that a follow-up work on top of a simple fix. Yeah. IIRC, as David suggested earlier, we can just check if a page is poisoned using PageHWPoison(). Perhaps we should move this check into pages_identical()? This would make it a central place to determine if pages are safe to access and merge ;) BTW, could you please keep me in the loop for the next version? Thanks, Lance > > [1] https://lore.kernel.org/all/20250922021458.68123-1-lance.yang@linux.d= ev/ > > -- > Cheers > > David / dhildenb > >