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b=Q261pOzqDy+B8Ff3jFanfTrvyKm/idwoi8pMCcZLKo778FlycP7l4gb8vqXlFIFc7 88ivA90+P1kxfFJb+iCmup+XTuzTIjHNCLlTSmSr3FJ8XnWzTwL3H2kNTkTwqpz8hr xXkK/ltoTpaxLwaycidA2l5yvWhiSW/LPgVkX5ZfOTPx6PckJujePtwGdfrGnVnv7E 4kKo00QcVJkXBuH7+Y1QWE9e0dRmqghOPAHff8HJ1Du0yxihOKjxbh9U0IGPcQdLDN ovKcH55oJJEODbR3xCnO20gApkJEPYT/aK/26PeaJ2xOyAjgoGB4swKj5uvJaACMg6 wEBQtVKrb78gw== Message-ID: <168ad406-f6b5-4623-adac-9f894e410e48@kernel.org> Date: Mon, 27 Jul 2026 16:20:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/5] Only free healthy pages in high-order has_hwpoisoned folio To: "Vlastimil Babka (SUSE)" , William Roche , Jiaqi Yan , linmiaohe@huawei.com, ljs@kernel.org, ziy@nvidia.com Cc: osalvador@kernel.org, harry.yoo@oracle.com, willy@infradead.org, osalvador@suse.de, jackmanb@google.com, hannes@cmpxchg.org, nao.horiguchi@gmail.com, tony.luck@intel.com, wangkefeng.wang@huawei.com, jane.chu@oracle.com, akpm@linux-foundation.org, muchun.song@linux.dev, liam@infradead.org, rientjes@google.com, duenwen@google.com, jthoughton@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, shuah@kernel.org, surenb@google.com, mhocko@suse.com, boudewijn@delta-utec.com References: <20260705180714.3708947-1-jiaqiyan@google.com> <85cb7ea8-8116-4092-8310-69b61eb8602c@kernel.org> <1dea7b3c-7740-474d-b9d4-cd2baf47f181@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 11415160009 X-Stat-Signature: zj9cmmw53t3itz4u3meghqf37isw8c1j X-Rspam-User: X-HE-Tag: 1785162066-193960 X-HE-Meta: U2FsdGVkX18aQevFonCKfSMVnVxpyJYN7qIx30Zjyb0I76C6Av0MTo5l9oEfpLQvKNvvzETmDlXCYfr0SWQKz+ZcSORkp3/5RKSxJHTe2gDojnsr42c0djTMs4kcCsH66nWzkQC9Q+41slixgCszNsWulsybaZBhvMIKMsOqVW7cRyjhXb3zD/9LmR4OjiqpHQ93kQ+WqWbTkgHhPRfjhEziCSBX7i1oL9h+PeMSvV0wnC06jTsu/8+FIqZeHtcDYZjtx1fDS6nqbZR71B2l1DqSO6NsUaR4EKo+b7mJY6rtrepXvqkMf+FsLgi6MtdJUXvxAdw7U9h0phH9+zG2sYVbrhxL1HAsFOcYjItdvMEq+FAT/TjPniVLy58iVRaQuAkBcRyYFZAtRoYiISZrxGvEeoNsuhkBTmOz/tq7SNG3Av5k+dcaThRm6/GoWie7q41Aj7wi1cgIugUM0bgcbWTUmsTbkyu9uAeAUSEq9n0GwDVQFoouSL6sl6NyHzbGZ8bQ+tNMqhGjdYBvyWPDuz8hLCmQgkqKjiiSLo4X0WMrOpdfDps/EUKeIL2+wdnQOf7PUYxR580c5lViJg+TR3f9YBwpWvFW4W2gtx1t2TJ01ZTg0IsAfeRDZzNlWFEyk0gYEh3bHrC1AWctdx2G3zVnOhgfZwrqu3M14MAbdys9v7aMJ3Sre5cre/+AbiPzrhh/MYMecUsFmEGfmDxJXfURTsfHsJaH3iR+3bPXI0d7nBroyqI7vIXWJbQ61PlD7LEy0eKPwAevnlJ6zGoHQfKpUmc+arHZaGndqs3RGaO6lx7fUMCFQokuGBz5keYZFPXTWdwdT9Kf8XZiq/8DYbt7u0YBlWWVG0hdyOvws0MPThOsEbS4XS6A5YgsQxAlt5WJF+Oko2hTBFPBPyEihe8WcVIEfde+smymCSeTHKxk9vQZaXabRPTvATDZ4QVAiZTE6e8UjqlR5RgqHEY cucBk4/l UGZoIiu/GH8G/oooLEsmQw6NZYJQjrYIa9KZCnbuWY0Zy9KPmDZmLFGnyX8zKHtSnWQxAPqXZTXfChdG9hYmnDjrgwEW8Qpk3uFJxexvyFPqF3CFqIO4dVLosUfMIp+VnxcYvnVHQpqrieGe+QpHf1JFvNAXPU3sbZ5tDn4uybhvbcv3KOEGAN9jw72BD8MjUjV2A2CqFKU/IjVE5aJAGqDg01/kjbFuuWt411Wuu4IpDg7X62CZqa+VVKJRsvGokOeZC5w82Q3Y0WvjiO9TwuUz9Pnb1POlqwLgZcMXIiO2BdWgWWeUFMNYFYjGh74K3YI9cy/6DriJz2rOGShELT+db+TErtbd41o+DI9qY+UQBv026yC4wTt0x2Vdk1ycVpnledIBYDfLtrZK+02DG0BdtVQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/22/26 10:27, Vlastimil Babka (SUSE) wrote: > On 7/17/26 15:06, William Roche wrote: >> On 7/17/26 12:18, David Hildenbrand (Arm) wrote: >>> >>> I still don't like the complexity of this, in particular, as we have different >>> mechanisms in the page allocator already to try handling this, >>> >>> We also do have cases where we set the hwpoison bit, while a page is just about >>> to get allocated from the buddy. So before we take it off the buddy, we might >>> just hand out the page. >>> >>> check_new_pages() seems to check for PageHWPoison() and make us not hand out >>> such pages. It's guarded by "check_pages" but it seems to do exactly what we are >>> looking for, now? >> >> >> Just adding a comment about this aspect: >> The check_new_pages() mechanism used by the __rmqueue functions should >> filter these pages out, but this has been disabled by default in 2023 >> with: >> [PATCH] mm, page_alloc: reduce page alloc/free sanity checks >> https://lore.kernel.org/all/20230216095131.17336-1-vbabka@suse.cz >> >> So it would need to be enabled back, taking some of the performance hit. >> (and I personally think that it has to be done) > > Would it truly fix the issue, or rather there would still be a race window > left where we check that there's no hwpoison flag in the re-enabled check, > and only then someone sets it? Why are we checking PageHWPoison at all then in check_new_page()? I think we created a mess. The PageHWPoison check is not just a "nice to have" sanity check for kernel bugs. So it should never have been optimized out that way before reworking the bigger picture. > > Also, can the hardware actually detect a problem with a page that nobody > accesses? I guess if yes, it's only in some corner cases. Yes, quite frequently I think. > > So I'm wary about penalizing the allocator paths again. I get the feeling that we don't have a proper plan on how to handle HWPoisoned pages. We should take a step back and discuss how we actually want to handle them instead of optimizing here and there and creating more of a mess. -- Cheers, David