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 83D0F1EB9E5 for ; Tue, 11 Mar 2025 05:28:06 +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=1741670888; cv=none; b=EYL0Fv+gJH0FPLpfw6AyhYD5Xglxo6J9I9KLUqaFyIRVNAr2JQl6P/D+aFFqiI9w03mYTIFy+2v2lGjYgdlG8KWFyOjdJEPq3DCHr9pdSssGHwvplFwnYAbaKSChgZXZ9lHLkERANqXm+Mv4IYChwLrv8+NKM8B+/sZVurSgxaE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741670888; c=relaxed/simple; bh=eKRlHLWaBspEoRQ8S57NlVWYi2I+xHjGl2BFk2h+y7U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lNHF7OxodecxvuvJttFssQjlo1lJ7zRBYyUg0zGTmNbvePWEJksVXxOoGtTDkVdVw8xqOTVKO7kHDn0nmbEpO6cRVFKYmOTmIZMtGNkwnDjYVeSMIWmaRnz0DesxfY9Y3G7ZOC1jbSD3E6maVvN6FTRNO+nFkSOxGmC+ALdzVxU= 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; 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 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 1734D1516; Mon, 10 Mar 2025 22:28:17 -0700 (PDT) Received: from [10.162.40.19] (a077893.blr.arm.com [10.162.40.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2EA103F694; Mon, 10 Mar 2025 22:28:03 -0700 (PDT) Message-ID: Date: Tue, 11 Mar 2025 10:58:00 +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 v1] mm: use ptep_get() instead of directly dereferencing pte_t* To: Ryan Roberts , Andrew Morton , Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250310140418.1737409-1-ryan.roberts@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20250310140418.1737409-1-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/10/25 19:34, Ryan Roberts wrote: > It is best practice for all pte accesses to go via the arch helpers, to > ensure non-torn values and to allow the arch to intervene where needed > (contpte for arm64 for example). While in this case it was probably safe > to directly dereference, let's tidy it up for consistency. > > Signed-off-by: Ryan Roberts > --- > mm/migrate.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 22e270f727ed..33a22c2d6b20 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -202,7 +202,7 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > return false; > VM_BUG_ON_PAGE(!PageAnon(page), page); > VM_BUG_ON_PAGE(!PageLocked(page), page); > - VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page); > + VM_BUG_ON_PAGE(pte_present(ptep_get(pvmw->pte)), page); > > if (folio_test_mlocked(folio) || (pvmw->vma->vm_flags & VM_LOCKED) || > mm_forbids_zeropage(pvmw->vma->vm_mm)) > -- > 2.43.0 > > LGTM. Reviewed-by: Anshuman Khandual