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[2001:1c00:3405:d100:b173:9aa6:5c2:3fe1]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-654535c49dbsm2583543a12.32.2026.01.16.06.12.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Jan 2026 06:12:07 -0800 (PST) From: Boudewijn van der Heide To: jiaqiyan@google.com Cc: akpm@linux-foundation.org, boudewijn@delta-utec.com, hannes@cmpxchg.org, jackmanb@google.com, linmiaohe@huawei.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, nao.horiguchi@gmail.com, osalvador@suse.de, surenb@google.com, vbabka@suse.cz, ziy@nvidia.com Subject: Re: [PATCH] mm/page_alloc: Fix freeing of failed-split poisoned compound pages Date: Fri, 16 Jan 2026 15:11:57 +0100 Message-ID: <20260116141157.29578-1-boudewijn@delta-utec.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 05EC118000A X-Stat-Signature: nst5e9cm77fk3pr1z9wq5kwtkpgitbry X-Rspam-User: X-HE-Tag: 1768572729-764874 X-HE-Meta: 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 Y7qspykQ aQHdL/7Gh0VSjt3WjJCEE+qbq7w/aol5oy76ABn+0xwGH5nI9cv/MgudNzE1dajiYOi6OJHLO7CIIXi6+jWcw9GyMBHBUBaGW24UMFQ06OlGGfmsKJY1ClJcjkNk9+Go9BkwovXUqkf8/yef6ms+MVZz1Tnrj6P47UzvER7oBeVR+3saZ+3zEje71dDeBgK8q8u+aAx2x2uTx6VB8FQ5Jpy6KX1cRCkQHol58BKacKVIrIcGERrN3MANcpbvapNbG1Ix4uGue3yX0d/BMpzoMvrdsHBwlGyTEmNS0OSkVWAQ5rwzKVgfaKBJYdqaxS0PDEcSwkiHikOrXicsGW4sdGAJD6WGxo/LAb0HeFdaw8nGCTQ5yjgccSrP9VuOMyFlP++vxOgnB0BZlAJQZyKYHwHKLTj2/WcyRwLkaSB96mupSfbGWEaYoL6KlT+MGn+GwZh0Syaw2GTcGAFCu9HrQxyQeeGcrsEY0dL4Ial9PpQium0nd8gy/oelSkajOdke7GYh6X3UHKjAgyTKHaiRLdycbqrP1pRNhArTjvVaz7Y1AT3GEp4hXS6p6UlB8aZMkGrKB9AE//0Th87pTJGpC9ajxS/2fviKknjzltb+yBGNn3w0++kQq9iaQIQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000813, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks Jiaqi for the feedback, that is very helpful. (and thanks Miaohe for connecting the issues.) After going through the memory_failure(), I can see it indeed puts the PG_HWPoison flag on the specific subpage pointer, and therefore my fix won't work as-is. > > > > Yes, this is also a problematic scenario for Hugetlb HugePage. And Jiaqi works on > > it now [1]. I think Jiaqi's patches might apply to THP scenario too. Add @Jiaqi to > > verify this. > > Yep, I think my work will also help solve the concern when > try_to_split_thp_page() fails. Your fix makes a lot of sense for hugetlb, as it linearly scans through all the pages. >From my understanding, your fix also provides the perfect architecture for also checking THP, though it doesn't yet cover the in-use THP case outlined. For THP I would need to trace the failed-split paths more carefully, to check where the equivalent path for THP would be. If there is work needed for THP, I'm happy to help. Would you prefer I work on THP support as a separate follow-up patch, after yours is merged, or do you prefer to integrate it in your patch series? > > > > [1]: https://lore.kernel.org/all/20260112004923.888429-1-jiaqiyan@google.com/ > > > > Thanks. > > . Thanks, Boudewijn