From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (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 C1A4C2C11FA; Fri, 26 Jun 2026 03:18:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782443891; cv=none; b=gXeCIlhjjFwykA/Z3bHDDvSNRaDSUpvfgtvOXiKFTvqhTAY8UUf3VG06iBFjj4UGpJKAIST07d1nQpOjP7oZtaJivBs4kL8Jyl3wL3thyQqf4Wg1Xan9GePzslNvN5jIAfQxrUtAcSyydUyrJnZ7z+biehF3WIgwApALeH1yezM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782443891; c=relaxed/simple; bh=SIrzBechw8pC861FiUBjGRdVk/FO+vaHDtpa4S4PW+o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pRE3TuV37FLqT30pwvjB7SyYUhsSLqlshSIPbQRvs3zn1Q6BSfcbuS8VQr18VlPQq7lRL8glS3Wrm4NBe6NXMqRlT8LCGDi0znu+XABBAOKy3OpxPN22bI/QQ28Kwj0G51cj1yUzdUyDGGpaIXTI8okbbmhFeSOcaQ9me++kNeQ= 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=oeeeVHxT; arc=none smtp.client-ip=95.215.58.176 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="oeeeVHxT" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782443886; 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=OZJmc3takRDK7jQCyQNoqz4XYBQ54vYpzBE2NdGeia8=; b=oeeeVHxTM1sDNbDtkvWfeWlWL81Q3QugP8nzSEd8pZBSgXF1GGvz6loEWo07SGCgjDI1dn zvkkgZVmV6zYGwHGOd53ypDtk5qJPYupHaWIx+YDFcl2/mIZyVDBjyKowQNpbf/CCz7YP6 VfhfTscE5s4qRXV3XgaRUnsRxJx/L4c= Date: Fri, 26 Jun 2026 11:17:05 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 1/5] 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, mel@csn.ul.ie, nao.horiguchi@gmail.com, ak@linux.intel.com, j-nomura@ce.jp.nec.com, pfalcato@suse.de, dave.hansen@intel.com, tglx@kernel.org, jpoimboe@kernel.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: <20260625112955.3254283-1-dev.jain@arm.com> <20260625112955.3254283-2-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: <20260625112955.3254283-2-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/6/25 19:29, 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 > 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); Thanks so much for the fix! I'm curious, though: why do we need to add a separate declaration for this function here? Thanks, Muchun > + > 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); >