From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f178.google.com (mail-lb0-f178.google.com [209.85.217.178]) by kanga.kvack.org (Postfix) with ESMTP id 6EA266B003A for ; Thu, 21 Aug 2014 17:51:59 -0400 (EDT) Received: by mail-lb0-f178.google.com with SMTP id c11so8691563lbj.37 for ; Thu, 21 Aug 2014 14:51:58 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out1.inet.fi. [62.71.2.232]) by mx.google.com with ESMTP id kd8si39676139lbc.28.2014.08.21.14.51.57 for ; Thu, 21 Aug 2014 14:51:57 -0700 (PDT) Date: Fri, 22 Aug 2014 00:51:47 +0300 From: "Kirill A. Shutemov" 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org