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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9081dd91080sm11772486d6.49.2026.07.28.17.39.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 17:39:32 -0700 (PDT) Date: Tue, 28 Jul 2026 20:39:29 -0400 From: Gregory Price To: "Matthew Wilcox (Oracle)" Cc: Andrew Morton , Jane Chu , linux-mm@kvack.org, Muchun Song , Oscar Salvador , David Hildenbrand , Miaohe Lin , Naoya Horiguchi , Jan Kara , linux-fsdevel@vger.kernel.org, Christian Brauner , Jiaqi Yan , stable@vger.kernel.org Subject: Re: [PATCH v7 01/13] memory-failure: Fix hardware poison check in unpoison_memory() again Message-ID: References: <20260728204409.3396238-1-willy@infradead.org> <20260728204409.3396238-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260728204409.3396238-2-willy@infradead.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 466B71C0009 X-Stat-Signature: oksqmew8s6ksead3kg446hk98p1816ci X-HE-Tag: 1785285574-190557 X-HE-Meta: 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 JQzOs1vE 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 28, 2026 at 09:43:53PM +0100, Matthew Wilcox (Oracle) wrote: > The earlier patch (6c54312f9689) that attempted to fix unpoison_memory() > was incorrect for hugetlb folios. Before a6fddef49eef, we checked > the head page for poison (which was correct for hugetlb and incorrect > for THP). We are currently incapable of unpoisoning pages (other than > the first page) in a hugetlb folio. > > Use is_page_hwpoison() which handles hugetlb pages sufficiently well for > this purpose. This is racy as we don't have a reference on the folio at > this point, but fixing that properly requires deeper surgery and this > is a CAP_SYS_ADMIN path only so this will do for the moment and can be > easily backported. It's no worse than the situation before a6fddef49eef. > > The other bug in a6fddef49eef is that we currently clear the HWPoison > flag on the precise page, which is wrong for hugetlb. Fix that too. > > Fixes: a6fddef49eef ("mm/memory-failure: convert unpoison_memory() to folios") > Cc: stable@vger.kernel.org > Cc: Miaohe Lin > Signed-off-by: Matthew Wilcox (Oracle) Just trying to wrap my head around the state before/after, assuming the following is correct then LGTM: prior: pfn_to_online_page(pfn) -> p = precise page PageHWPoison(page) -> checks precise page. Poison for hugetlb is only set only on the head, so bug. after: is_page_hwpoison(page) -> checks precise page AND head (if hugetlb) p = folio->page -> now TestClearPageHWPoison() explicitly clears the head page poison if hugetlb Reviewed-by: Gregory Price (Meta)