From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (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 71D2635B650 for ; Thu, 2 Jul 2026 08:47:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782982063; cv=none; b=Xh7tqWTZpCQUEE6dIt+nAR/a11iJqkMCVVkPT4RclFH0YP61kMhqxCqaCqlWiakwQK0XKbMj97IROCXqeWRhRTcHxqxraA1rwZIP9BjDinLMxPQNE0Fmmfulb1LHxN+oCf3amupGnKPYFVv01sAi+bhrxwOoAEb88qqVWz0Gppk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782982063; c=relaxed/simple; bh=c0d8lIGwWhqUE/QJk4uCY/3fttioh0Q0bV69uMJ9tyM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QWUvo3RFymyFK2inJU0fpkgH0DvO81wZdAR9t1NgsdpAfO2Y1oNxQtpEkx9M/uPS9+9QHX9RqmvNnGj0IlDWhRtmUeNRjlU9aRI+Md0PJCH4+GeInmGcSlh6fvxR2R98trfFXGOm78+fJinlBGor03xUftEfBwTLFBv0QbIZzpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=CeY7Yl2Q; arc=none smtp.client-ip=95.215.58.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="CeY7Yl2Q" Message-ID: <97a43d82-28c2-4f98-ad74-fe05ed9f0297@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782982049; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=k0OA6sDR9xVrofWsz20wyHhFk3GqcE2ce4sWlpq82E8=; b=CeY7Yl2QeKZhrbQj/DcuVaDk/ScIJ/I13EQpZ8mQWaTSWVTAnJI6dr9QSnz88wDdAg8sKv Xt0Xi5Hd5b9ixMNZeCeiv8WObh/juzMGC6+hdTsDG80pj5Ut11tptk+UKPF6hyl/40jjAo Se6oTrt1q3oy4yS28IgmbRN4YnIsWTU= Date: Thu, 2 Jul 2026 16:47:10 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2 2/6] mm/rmap: use huge_ptep_get() in try_to_unmap_one() To: Dev Jain 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, 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, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, david@kernel.org, liam@infradead.org References: <20260702051341.126509-1-dev.jain@arm.com> <20260702051341.126509-3-dev.jain@arm.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20260702051341.126509-3-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/7/2 13:13, 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); > + Maybe I didn't express my thoughts clearly in the first version, let me explain in more detail. We should define this stub as a no-op for !CONFIG_HUGETLB_PAGE (like set_huge_pte_at, that is why I mentioned 5d4af6195c87c6 for your reference in your previous version). Currently, you've added a declaration, but the function itself doesn't actually exist, which seems quite strange to me. Muchun, Thanks. > 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. > - */ > - 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. > + */ > + pteval = ptep_get(pvmw.pte); > + } > if (likely(pte_present(pteval))) { > pfn = pte_pfn(pteval); > } else { > @@ -2110,7 +2115,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > } > > subpage = folio_page(folio, pfn - folio_pfn(folio)); > - address = pvmw.address; > anon_exclusive = folio_test_anon(folio) && > PageAnonExclusive(subpage); >