From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D2CC9C43458 for ; Thu, 2 Jul 2026 15:35:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jWa1mD+awYvcVqO7NB5NDH/ijt/TFGs11SlmfzyMrnY=; b=bbklaC3yEozHuMEPdBRi0PBHtB 5y9gtx2S9ARSJUjrNsorFoKlCTXvkYkI1UtoHLSn1g8QyI4nLXbAsIf3qixRV2JD7KPo1vc6Eveer Enf1XVNE2JRWVgzrB99MfRNU5PWlLdoU7XGpVm2GzpWu3qW5MTpdC/x77nWrcVrf29eEXBP8VJI5f rlxUNh0B0TfmzzMAiVGduvhO+pRTHdqFzIO1pbOT1SNRKLay3cPFXisWJqm4dpyu2qNf08SspQYeN lG1xGaN65AWSyX6jJB5W0/gHW96KEH7Ev/ih87Q417dVDMz1m0cHBic1yX21Ggc+ErYY8ThfHRnox OaZssjhQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfJRU-00000004pWT-2Lxc; Thu, 02 Jul 2026 15:35:08 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfJRT-00000004pVt-0A25 for linux-arm-kernel@lists.infradead.org; Thu, 02 Jul 2026 15:35:07 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C600F4356A; Thu, 2 Jul 2026 15:35:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6ABFF1F000E9; Thu, 2 Jul 2026 15:34:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783006506; bh=jWa1mD+awYvcVqO7NB5NDH/ijt/TFGs11SlmfzyMrnY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=claYiCGD9+iGsb3rEHrI1s5HJg2hkS7W6gL8omu35jx7x6oqejSN3G4l7/5wm7Oj8 +qeUOcSoyvFJPDTJquyp36FHneu5xD9PqAyLHKJcQ+P3eTzJg10elubGWbYbJr+tvk gEE7trLBICmQyG4GF4bSPPqOoz8r1KexO9NQFWpt3u0Qf8T4/i/JJfkd3SpHnFKz99 RX6qVFtcgpOs+c+omD5H0aJsah5hYR2/8Ml0K83F+CITI6tNy81EbWhYtG4d4EAkVL yNTim2+Lm0L3zEKKV5p6v+OojCOKZ+TZsWnkiFcAAN0kVhGppFbuEVQCf5lkvEZkm2 Ixf8nfTRbGYxw== Message-ID: <38a23f8c-56c4-43a2-a3ed-bf7d4f784cda@kernel.org> Date: Thu, 2 Jul 2026 17:34:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/6] mm/rmap: use huge_ptep_get() in try_to_migrate_one() To: Dev Jain , muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcampbell@nvidia.com, apopple@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, j-nomura@ce.jp.nec.com, nao.horiguchi@gmail.com, ak@linux.intel.com, mel@csn.ul.ie, pfalcato@suse.de, jpoimboe@kernel.org, dave.hansen@intel.com, tglx@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org References: <20260702051341.126509-1-dev.jain@arm.com> <20260702051341.126509-4-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-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/2/26 07:13, Dev Jain wrote: > try_to_migrate_one() is used by folio migration to replace a present > mapping with a migration entry. For hugetlb folios, page_vma_mapped_walk() > returns the pte pointer to the hugetlb folio in pvmw.pte, but the code > reads the huge pte entry with ptep_get(). > > On arches which provide their own huge_ptep_get() to dereference a huge > pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present() > etc to misbehave. > > It is not clear whether this has a trivially visible effect to userspace. > > Use huge_ptep_get() to dereference a huge pte pointer. > > Commit a98a2f0c8ce1 copied the bug from try_to_unmap_one into > try_to_migrate_one. > > Fixes: a98a2f0c8ce1 ("mm/rmap: split migration into its own function") > Cc: stable@vger.kernel.org > Acked-by: Muchun Song > Signed-off-by: Dev Jain > --- > mm/rmap.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index aa8a254efaecc..abc3a44baaa3d 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2505,11 +2505,16 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > /* Unexpected PMD-mapped THP? */ > VM_BUG_ON_FOLIO(!pvmw.pte, folio); > > - /* > - * Handle PFN swap PTEs, such as device-exclusive ones, that > - * actually map pages. > - */ > - pteval = ptep_get(pvmw.pte); > + address = pvmw.address; > + if (folio_test_hugetlb(folio)) { > + pteval = huge_ptep_get(mm, address, pvmw.pte); > + } else { > + /* > + * Handle PFN swap PTEs, such as device-exclusive ones, > + * that actually map pages. > + */ Again, the comment is related to the pte_present() handling, so best to move it down there. Apart from that LGTM. -- Cheers, David