From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261543AbVHBPa7 (ORCPT ); Tue, 2 Aug 2005 11:30:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261566AbVHBPa7 (ORCPT ); Tue, 2 Aug 2005 11:30:59 -0400 Received: from smtp.osdl.org ([65.172.181.4]:13272 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S261543AbVHBPa5 (ORCPT ); Tue, 2 Aug 2005 11:30:57 -0400 Date: Tue, 2 Aug 2005 08:30:37 -0700 (PDT) From: Linus Torvalds To: Martin Schwidefsky cc: Andrew Morton , Robin Holt , Hugh Dickins , linux-kernel , linux-mm@kvack.org, Ingo Molnar , Nick Piggin , Roland McGrath Subject: Re: [patch 2.6.13-rc4] fix get_user_pages bug In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2 Aug 2005, Martin Schwidefsky wrote: > > Why do we require the !pte_dirty(pte) check? I don't get it. If a writeable > clean pte is just fine then why do we check the dirty bit at all? Doesn't > pte_dirty() imply pte_write()? A _non_writable and clean pty is _also_ fine sometimes. But only if we have broken COW and marked it dirty. > With the additional !pte_write(pte) check (and if I haven't overlooked > something which is not unlikely) s390 should work fine even without the > software-dirty bit hack. No it won't. It will just loop forever in a tight loop if somebody tries to put a breakpoint on a read-only location. On the other hand, this being s390, maybe nobody cares? Linus