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t=1781093616; bh=tW9fi4n70DTe0jKQWNlCCgMLZ+31F8mfQuXRgyJyVkY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Rci2HN3OwO1ymyDTMsxaimtVz61j1SVR5a1HNNnAqYipxSKlcNyVnY3LL+c5Pb/ax uBXF/JllYXjV1DVOaRBnh6s6SnErpWvoVYAsddnG9UGfZJnuF+PDj2nAaXDYFkidy+ ZqfMdTghIj2OJjDPjMVdGXwFQeYLHf9l+dyd6KkK3ncxNz6WjUshmZdJZC1LCOVHw7 tFHf5lAaNXIDo5fpZ2S7zTjQUaO2toCeTGXj1agHlEy0YTEcJAHfizQ2eayRRWuNtz thsa2u1gelx/VznzPbkX5udLYmLm7BIIKWuIFmfvoL4OAdjpQCvp1bCn22vTlbUY3K fNtm7sbTRzEiw== Message-ID: <60082692-b7f7-45a4-bcfb-0df0b6eb6329@kernel.org> Date: Wed, 10 Jun 2026 14:13:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 01/12] mm/rmap: convert page -> folio for hwpoison checks To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260526063635.61721-1-dev.jain@arm.com> <20260526063635.61721-2-dev.jain@arm.com> 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-Queue-Id: 82632C0007 X-Stat-Signature: z1i6yk67w6jc94o5tq9wm9yowpwg7hce X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1781093617-808201 X-HE-Meta: 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 zbrl8A2v PtpQt8fJYNQK7vOKJD6kITAd6XLryPnKk77X2Z9SIDZIxJBIUDmHvkLp5AUg41Bcgo/TpiGLcw+HUj3BzJwIT/keFrnF14EU56EiyPLPc0WO4uai7lLjKIZY1FIRtelyvTdsXQQE1kDj4w1oHtTPtpSQdHbhnkDIbQ2/KxdeZvn1480r2h/Cr3VvTCC1zVIfKBUAru4UYJPisIze/cJg60sKgfpd8ND3d8JYGynzExuEYc1L3Eg3NYGk5DJoMxYATtMCh Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/10/26 09:02, Dev Jain wrote: > > > On 09/06/26 7:14 pm, David Hildenbrand (Arm) wrote: >> On 5/26/26 08:36, Dev Jain wrote: >>> If any page of a folio is poisoned, try_to_unmap() is called with the >>> intent to remove any mappings pointing to any part of the folio. >>> >>> Therefore, an hwpoison check on a single page does not make sense >>> (although everything works out because the memory-failure path sets >>> hwpoison on the head page too). Convert these checks to check whether >>> the folio has at least one hwpoisoned page. >> >> I think the reasoning is different and should better be described: >> >> 1) For hugetlb, we will always get subpage == head page (single PTE -> first PFN). >> >> try_memory_failure_hugetlb()->try_memory_failure_hugetlb()->hugetlb_update_hwpoison() >> will do the folio_test_set_hwpoison(). >> >> folio_test_set_hwpoison() is the same as setting it on the head page. >> >> For hugetlb, subpage==headpage >> >> That's why PageHWPoison(subpage) used to work. >> >> >> 2) try_to_unmap() cannot handle large folios (besides hugetlb folios). >> >> unmap_poisoned_folio() spells that out. That's why subpage==headpage right now. > > Should have mentioned: subpage != headpage for contpte mapped hugetlb folios > on arm64. No, hugetlb code always walks "logical" PTEs, not physical ones. So it will walk each hugetlb folio only once, and always hit the head page. That is, for cont-pte/pmd, it will always return the first PTE in the cont-pte group. See page_vma_mapped_walk()->hugetlb_walk machinery. -- Cheers, David