From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f170.google.com (mail-wi0-f170.google.com [209.85.212.170]) by kanga.kvack.org (Postfix) with ESMTP id 3BA676B0038 for ; Thu, 19 Mar 2015 16:03:11 -0400 (EDT) Received: by wibg7 with SMTP id g7so127521964wib.1 for ; Thu, 19 Mar 2015 13:03:10 -0700 (PDT) Received: from jenni2.inet.fi (mta-out1.inet.fi. [62.71.2.195]) by mx.google.com with ESMTP id l3si3762268wjy.173.2015.03.19.13.03.09 for ; Thu, 19 Mar 2015 13:03:09 -0700 (PDT) Date: Thu, 19 Mar 2015 22:02:52 +0200 From: "Kirill A. Shutemov" Subject: Re: [PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages Message-ID: <20150319200252.GA13348@node.dhcp.inet.fi> References: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> <1426784902-125149-6-git-send-email-kirill.shutemov@linux.intel.com> <550B15A0.9090308@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <550B15A0.9090308@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , Hugh Dickins Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jaroslav Kysela , Takashi Iwai , alsa-devel@alsa-project.org On Thu, Mar 19, 2015 at 11:29:52AM -0700, Dave Hansen wrote: > On 03/19/2015 10:08 AM, Kirill A. Shutemov wrote: > > The odd exception is PG_dirty: sound uses compound pages and maps them > > with PTEs. NO_COMPOUND triggers VM_BUG_ON() in set_page_dirty() on > > handling shared fault. Let's use HEAD for PG_dirty. > > Can we get the sound guys to look at this, btw? It seems like an odd > thing that we probably don't want to keep around, right? CC: +sound guys I'm not sure what is right fix here. At the time adding __GFP_COMP was a fix: see f3d48f0373c1. Other odd part about __GFP_COMP here is that we have ->_mapcount in tail pages to be used for both: mapcount of the individual page and for gup pins. __compound_tail_refcounted() doesn't recognize that we don't need tail page accounting for these pages. Hugh, I tried to ask you about the situation several times (last time on the summit). Any comments? -- 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