From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F5B2406271 for ; Wed, 10 Jun 2026 12:13:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781093618; cv=none; b=N8cPPmzZ6X6GCZrcQeMXuKJAVvEpdHyhAzk+1nqdneUXFyAHLwJKSj2AHcMQ0bSpvgk99vKwGGXtcVkp2uNvtS9YFIVt0ARrGJJ12t0i7UZs/Z9FxGmV31F1N4I+7kpPJ5U9bBxMy/VcqZceIrTVq0+LgEwm3iv4HBQuU76cQD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781093618; c=relaxed/simple; bh=2VnPNTHaSwNSb//FfurFtTwUWc7OYVUCNzI0dM/kp5Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SdLabT8UnflrPFdlXuRJIdZul9TZHk/jgeQGQ2NwkJvJITMGX1j3wvKaghQoptVRCTS48/mqLXci3HJo1G67utFsky9MerPBZBDkkY0NVLqn+INeoXyTczQBxbuuIgRWa1GJAU0Cm14eCzRjHj69QhFovNObr4hi7itUqd1iX4M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Rci2HN3O; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Rci2HN3O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAFC41F00893; Wed, 10 Jun 2026 12:13:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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