From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755037AbaHUWCD (ORCPT ); Thu, 21 Aug 2014 18:02:03 -0400 Received: from mta-out1.inet.fi ([62.71.2.228]:55304 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754508AbaHUWCB (ORCPT ); Thu, 21 Aug 2014 18:02:01 -0400 Date: Fri, 22 Aug 2014 00:51:47 +0300 From: "Kirill A. Shutemov" To: Peter Feiner Cc: Cyrill Gorcunov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pavel Emelyanov , Jamie Liu , Hugh Dickins , Naoya Horiguchi , Andrew Morton , Magnus Damm Subject: Re: [PATCH] mm: softdirty: write protect PTEs created for read faults after VM_SOFTDIRTY cleared Message-ID: <20140821215147.GA15482@node.dhcp.inet.fi> References: <1408571182-28750-1-git-send-email-pfeiner@google.com> <20140820234543.GA7987@node.dhcp.inet.fi> <20140821193737.GC16042@google.com> <20140821205115.GH14072@moon> <20140821213942.GA15218@node.dhcp.inet.fi> <20140821214601.GD16042@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140821214601.GD16042@google.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 21, 2014 at 05:46:01PM -0400, Peter Feiner wrote: > On Fri, Aug 22, 2014 at 12:39:42AM +0300, Kirill A. Shutemov wrote: > > On Fri, Aug 22, 2014 at 12:51:15AM +0400, Cyrill Gorcunov wrote: > > > > Looks good to me. > > > > Would you mind to apply the same pgprot_modify() approach on the > > clear_refs_write(), test and post the patch? > > > > Feel free to use my singed-off-by (or suggested-by if you prefer) once > > it's tested (see merge case below). > > Sure thing :-) > > > One thing: there could be (I haven't checked) complications on > > vma_merge(): since vm_flags are identical it assumes that it can reuse > > vma->vm_page_prot of expanded vma. But VM_SOFTDIRTY is excluded from > > vm_flags compatibility check. What should we do with vm_page_prot there? > > Since the merged VMA will have VM_SOFTDIRTY set, it's OK that it's vm_page_prot > won't be setup for write notifications. For the purpose of process migration, > you'll just get some false positives, which is tolerable. Right. But should we disable writenotify back to avoid exessive wp-faults if it was enabled due to soft-dirty (the case when expanded vma is soft-dirty)? -- Kirill A. Shutemov