From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933506AbXCZFyH (ORCPT ); Mon, 26 Mar 2007 01:54:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932760AbXCZFyH (ORCPT ); Mon, 26 Mar 2007 01:54:07 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:63842 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933506AbXCZFyE (ORCPT ); Mon, 26 Mar 2007 01:54:04 -0400 X-AuditID: d80ac287-976cabb000000c42-09-46075ff93611 Date: Mon, 26 Mar 2007 06:53:50 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: David Rientjes cc: Andrew Morton , Ingo Molnar , Zachary Amsden , linux-kernel@vger.kernel.org Subject: Re: [patch -mm 1/2] i386: add ptep_test_and_clear_{dirty,young} In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-OriginalArrivalTime: 26 Mar 2007 05:54:01.0260 (UTC) FILETIME=[272A0EC0:01C76F6B] X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 25 Mar 2007, David Rientjes wrote: > Add ptep_test_and_clear_{dirty,young} to i386. They advertise that they > have it and there is at least one place where it needs to be called > without the page table lock: to clear the accessed bit on write to Without the page table lock?? > /proc/pid/clear_refs. > > ptep_clear_flush_{dirty,young} are updated to use the new functions. The > overall net effect to current users of ptep_clear_flush_{dirty,young} is > that we introduce an additional branch. We need to Cc Zach on this: git blame indicates it was he who replaced i386's ptep_test_and_clear_{dirty,young} by that "We don't actually have these" comment - it looks a bit as if what you want to do might violate the assumptions he wants to make, but I don't grasp it. Hugh > > Cc: Hugh Dickins > Cc: Ingo Molnar > Signed-off-by: David Rientjes > --- > include/asm-i386/pgtable.h | 25 +++++++++++++++++-------- > 1 files changed, 17 insertions(+), 8 deletions(-) > > diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h > --- a/include/asm-i386/pgtable.h > +++ b/include/asm-i386/pgtable.h > @@ -283,12 +283,23 @@ do { \ > } \ > } while (0) > > -/* > - * We don't actually have these, but we want to advertise them so that > - * we can encompass the flush here. > - */ > #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY > +static inline int ptep_test_and_clear_dirty(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep) > +{ > + if (!pte_dirty(*ptep)) > + return 0; > + return test_and_clear_bit(_PAGE_BIT_DIRTY, &ptep->pte_low); > +} > + > #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG > +static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep) > +{ > + if (!pte_young(*ptep)) > + return 0; > + return test_and_clear_bit(_PAGE_BIT_ACCESSED, &ptep->pte_low); > +} > > /* > * Rules for using ptep_establish: the pte MUST be a user pte, and > @@ -305,9 +316,8 @@ do { \ > #define ptep_clear_flush_dirty(vma, address, ptep) \ > ({ \ > int __dirty; \ > - __dirty = pte_dirty(*(ptep)); \ > + __dirty = ptep_test_and_clear_dirty((vma), (address), (ptep)); \ > if (__dirty) { \ > - clear_bit(_PAGE_BIT_DIRTY, &(ptep)->pte_low); \ > pte_update_defer((vma)->vm_mm, (address), (ptep)); \ > flush_tlb_page(vma, address); \ > } \ > @@ -318,9 +328,8 @@ do { \ > #define ptep_clear_flush_young(vma, address, ptep) \ > ({ \ > int __young; \ > - __young = pte_young(*(ptep)); \ > + __young = ptep_test_and_clear_young((vma), (address), (ptep)); \ > if (__young) { \ > - clear_bit(_PAGE_BIT_ACCESSED, &(ptep)->pte_low); \ > pte_update_defer((vma)->vm_mm, (address), (ptep)); \ > flush_tlb_page(vma, address); \ > } \