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Thu, 30 Oct 2025 19:19:55 -0700 (PDT) Date: Fri, 31 Oct 2025 02:19:54 +0000 From: Wei Yang To: Zi Yan Cc: linmiaohe@huawei.com, david@redhat.com, jane.chu@oracle.com, kernel@pankajraghav.com, akpm@linux-foundation.org, mcgrof@kernel.org, nao.horiguchi@gmail.com, Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , "Matthew Wilcox (Oracle)" , Wei Yang , Yang Shi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH v4] mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split to >0 order Message-ID: <20251031021954.ba2pymy2hjvgzohf@master> Reply-To: Wei Yang References: <20251023030521.473097-1-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251023030521.473097-1-ziy@nvidia.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2C2DB1C0004 X-Stat-Signature: pfyaqpgbspq3ca8h58iyafc5g88m69c3 X-Rspam-User: X-HE-Tag: 1761877197-994961 X-HE-Meta: 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 RmGJdIFq /9fB0V/n5DYcCwdWoRlcPH5bCPKFIbM4ctgZMOlmG9fUQ8cciShwzTczuCzZFPQT1Tgd0gkfTzcD97FNhtkkmBZMDwYqOPrZmWJDQ3WRYQuTLicCHdMt0CvnW9innM70J0K0heb1VAwyujlmGMxKlyMC8f96NDjGBQhmvtVsvirvkJZNxIrcJpkq2kV31x3MLiIfKNyvCI+N4Kq40lC4Wp5WklZKDqFtM3jozjRBC0Avg4DQ6PQlRJFduThsrSF3ipRhn4O88tTwgPMGvRAzsWzEQJkZswTdmxTO1kEm5CPtuaK00t0hfMuiQkH8WE64vnBkt 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 Wed, Oct 22, 2025 at 11:05:21PM -0400, Zi Yan wrote: >folio split clears PG_has_hwpoisoned, but the flag should be preserved in >after-split folios containing pages with PG_hwpoisoned flag if the folio is >split to >0 order folios. Scan all pages in a to-be-split folio to >determine which after-split folios need the flag. > >An alternatives is to change PG_has_hwpoisoned to PG_maybe_hwpoisoned to >avoid the scan and set it on all after-split folios, but resulting false >positive has undesirable negative impact. To remove false positive, caller >of folio_test_has_hwpoisoned() and folio_contain_hwpoisoned_page() needs to >do the scan. That might be causing a hassle for current and future callers >and more costly than doing the scan in the split code. More details are >discussed in [1]. > >This issue can be exposed via: >1. splitting a has_hwpoisoned folio to >0 order from debugfs interface; >2. truncating part of a has_hwpoisoned folio in > truncate_inode_partial_folio(). > >And later accesses to a hwpoisoned page could be possible due to the >missing has_hwpoisoned folio flag. This will lead to MCE errors. > >Link: https://lore.kernel.org/all/CAHbLzkoOZm0PXxE9qwtF4gKR=cpRXrSrJ9V9Pm2DJexs985q4g@mail.gmail.com/ [1] >Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages") >Cc: stable@vger.kernel.org >Signed-off-by: Zi Yan Reviewed-by: Wei Yang -- Wei Yang Help you, Help me