From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751717AbdFGO5K (ORCPT ); Wed, 7 Jun 2017 10:57:10 -0400 Received: from foss.arm.com ([217.140.101.70]:33762 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751410AbdFGO5J (ORCPT ); Wed, 7 Jun 2017 10:57:09 -0400 Date: Wed, 7 Jun 2017 15:57:16 +0100 From: Will Deacon To: Catalin Marinas Cc: Punit Agrawal , David Woods , steve.capper@arm.com, tbaicar@codeaurora.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, manoj.iyer@canonical.com Subject: Re: [PATCH v2 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries Message-ID: <20170607145715.GI30263@arm.com> References: <20170517152336.6052-1-punit.agrawal@arm.com> <20170517152336.6052-2-punit.agrawal@arm.com> <20170607134731.GG30263@arm.com> <20170607143037.ovyo5pxywty2r6as@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170607143037.ovyo5pxywty2r6as@localhost> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 07, 2017 at 03:30:37PM +0100, Catalin Marinas wrote: > On Wed, Jun 07, 2017 at 02:47:32PM +0100, Will Deacon wrote: > > On Wed, May 17, 2017 at 04:23:34PM +0100, Punit Agrawal wrote: > > > --- a/arch/arm64/mm/hugetlbpage.c > > > +++ b/arch/arm64/mm/hugetlbpage.c > > > @@ -136,36 +136,27 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) > > > { > > > pgd_t *pgd; > > > pud_t *pud; > > > - pmd_t *pmd = NULL; > > > - pte_t *pte = NULL; > > > + pmd_t *pmd; > > > > > > pgd = pgd_offset(mm, addr); > > > pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd); > > > if (!pgd_present(*pgd)) > > > return NULL; > > > + > > > pud = pud_offset(pgd, addr); > > > - if (!pud_present(*pud)) > > > + if (pud_none(*pud)) > > > return NULL; > > > > Do you actually need this special case? > > > > > - > > > - if (pud_huge(*pud)) > > > + /* swap or huge page */ > > > + if (!pud_present(*pud) || pud_huge(*pud)) > > > > ... couldn't you just add a '|| pud_none(*pud)' in here? > > > > > return (pte_t *)pud; > > But then you no longer return NULL if *pud == 0. Does that actually matter? The bits of hugetlb code I looked at will deferenced the returned pud and handle the huge_pte_none case correctly. Will