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 4CBFEC43458 for ; Fri, 3 Jul 2026 05:30:33 +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=V4iIBY89FDo1UzdzB/uBcAQK/RPNiJ0sNDuJsScMG6k=; b=nOALjs/ItsV55hqI412ISaqQel BEuoGI7dD34H0/adB+sVwQU+AufsdZX5ijIDqVC6tHwwv2ZntF9k30VimuSV1Mq/XUcYQqznoEcjH e9AVa4Sior/++OdAFmMks4Jag7ENf4of/738ETMLL9HGywoCOUv8Wv9dgT1K38ZYjYfBozmROItV3 uXAEIl1lFfyJ6Ub0+cxlYsra28325liNIO0SaRuU2cEsvmZwHzInZ35C2T7OGhua1l83CuTkAGs5K oGKHrCAApIR39V2pWOqnqpHpZ5BzLP153qEm/xyhpRjKbQuSio64VtvDI+B5UuntQYxh1nhXQeHaq iOl8FUFw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfWTp-000000064C9-2lYM; Fri, 03 Jul 2026 05:30:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wfWTk-000000064Bl-2jTj for linux-arm-kernel@lists.infradead.org; Fri, 03 Jul 2026 05:30:23 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 22BD51D14; Thu, 2 Jul 2026 22:30:09 -0700 (PDT) Received: from [10.164.19.15] (unknown [10.164.19.15]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5C07E3F673; Thu, 2 Jul 2026 22:30:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783056613; bh=UFr9Wdq1njDGvt6poz4+T8rHJby7UnZmUIqtj/UdkVQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YtDDG9+n6E2IK/NpzkunB8X0k+Xu7zlG2Mf5SenOvVidxgMMYHZg26V+CGrvrecH6 Phd+lP85qg5BeenR7AD3hjvJsYiHZNu7FLsqlY3Hi9oaCyU7BotAHiGSuPCbr1ubOC BlLtVt9t0QMmj5jX0Bv5+rJ7pk5lVZwwL53kf6vU= Message-ID: <1b1f6281-2a46-4811-bbea-24a666c0a772@arm.com> Date: Fri, 3 Jul 2026 11:00:01 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/6] mm/rmap: use huge_ptep_get() in try_to_unmap_one() To: "David Hildenbrand (Arm)" , 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> <20260702051341.126509-3-dev.jain@arm.com> <00d6e0fb-dcba-45d5-98c0-f5ed81604ca0@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <00d6e0fb-dcba-45d5-98c0-f5ed81604ca0@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260702_223020_852814_021E9056 X-CRM114-Status: GOOD ( 17.64 ) 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 02/07/26 9:02 pm, David Hildenbrand (Arm) wrote: > On 7/2/26 07:13, Dev Jain wrote: >> try_to_unmap_one() handles hugetlb folios when memory failure needs >> to replace a poisoned hugetlb mapping with a hwpoison entry. In that >> case page_vma_mapped_walk() returns the pte pointer to the hugetlb folio >> in pvmw.pte, but the code reads it 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. >> >> Just use huge_ptep_get() for dereferencing a huge pte pointer. >> >> Fixes: c7ab0d2fdc84 ("mm: convert try_to_unmap_one() to use page_vma_mapped_walk()") >> Cc: stable@vger.kernel.org >> Reported-by: David Hildenbrand >> Signed-off-by: Dev Jain >> --- >> include/linux/hugetlb.h | 3 +++ >> mm/rmap.c | 16 ++++++++++------ >> 2 files changed, 13 insertions(+), 6 deletions(-) >> >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 2abaf99321e90..fdb7bdf7645c5 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -1261,6 +1261,9 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm) >> { >> } >> >> +pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep); > > Two tabs, or just in a single line. > > If others prefer a stub, I don't care. This here is shortest to let the linker > bail out. > >> + >> static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma, >> unsigned long addr, pte_t *ptep) >> { >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 1c77d5dc06e9f..aa8a254efaecc 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -2095,11 +2095,16 @@ static bool try_to_unmap_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. >> - */ > > That comment now actually belongs above the pte_present() check below. Oops I mindlessly just copied the comment. I will then rather put it in the else block which gets the pfn from the softleaf, that is the most appropriate. > >