From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id C02696B0031 for ; Tue, 15 Oct 2013 15:28:56 -0400 (EDT) Received: by mail-pa0-f45.google.com with SMTP id rd3so9542107pab.18 for ; Tue, 15 Oct 2013 12:28:56 -0700 (PDT) Date: Tue, 15 Oct 2013 15:28:50 -0400 From: Naoya Horiguchi Message-ID: <1381865330-8nb86ucy-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <20131015185510.GH3479@redhat.com> References: <20131015143407.GE3479@redhat.com> <20131015144827.C45DDE0090@blue.fi.intel.com> <20131015185510.GH3479@redhat.com> Subject: Re: mm: fix BUG in __split_huge_page_pmd Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Hugh Dickins , "Kirill A. Shutemov" , Andrew Morton , David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, Oct 15, 2013 at 08:55:10PM +0200, Andrea Arcangeli wrote: > On Tue, Oct 15, 2013 at 10:53:10AM -0700, Hugh Dickins wrote: > > I'm afraid Andrea's mail about concurrent madvises gives me far more > > to think about than I have time for: seems to get into problems he > > knows a lot about but I'm unfamiliar with. If this patch looks good > > for now on its own, let's put it in; but no problem if you guys prefer > > to wait for a fuller solution of more problems, we can ride with this > > one internally for the moment. > > I'm very happy with the patch and I think it's a correct fix for the > COW scenario which is deterministic so the looping makes a meaningful > difference for it. If we wouldn't loop, part of the copied page > wouldn't be zapped after the COW. I like this patch, too. If we have the loop in __split_huge_page_pmd as suggested in this patch, can we assume that the pmd is stable after __split_huge_page_pmd returns? If it's true, we can remove pmd_none_or_trans_huge_or_clear_bad check in the callers side (zap_pmd_range and some other page table walking code.) Naoya Horiguchi -- 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