From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0014A33F58D; Fri, 3 Jul 2026 05:30:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783056622; cv=none; b=Mr1zp6D+jzZMKz6j4ciR6xzXnRVjwJL1tt0hcP9qo0iuQj6V09g+kcTWsoyU0Rmg/mlaNJoCtjn1FCBsIq00J3UzE/OrRUYTLFqaQUEDp8zvqjU8yYd+dN/J/AiwOiFvCupM2DFs8zKq5XwJAKsGwHfLBGu5kxtPq7nwIdRX+FI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783056622; c=relaxed/simple; bh=UFr9Wdq1njDGvt6poz4+T8rHJby7UnZmUIqtj/UdkVQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TNOAMwYTUzxebshMMi7qKrIomBpEwNj84XX0yQHH3AbSYS7FHkM2lBNg+qq0NbYEmq7zJmV0LPxstwOWsxLUmdeDqu3HwYRL1wu8xB09r/PidWKZ46IeQCtkMsM1TpkE95aMat/T7XBkYevWW56HSG4milpCk+SAthe+a9PdZzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=YtDDG9+n; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="YtDDG9+n" 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 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 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 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. > >