From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 053A76B00B1 for ; Tue, 26 Jan 2010 14:48:49 -0500 (EST) Message-ID: <4B5F46FA.4030509@redhat.com> Date: Tue, 26 Jan 2010 14:48:10 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 04 of 31] update futex compound knowledge References: <948638099c17d3da3d6f.1264513919@v2.random> <4B5F1460.7030106@redhat.com> <20100126171032.GS30452@random.random> In-Reply-To: <20100126171032.GS30452@random.random> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Izik Eidus , Hugh Dickins , Nick Piggin , Mel Gorman , Andi Kleen , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , Andrew Morton , bpicco@redhat.com, Christoph Hellwig , KOSAKI Motohiro List-ID: On 01/26/2010 12:10 PM, Andrea Arcangeli wrote: > On Tue, Jan 26, 2010 at 11:12:16AM -0500, Rik van Riel wrote: >> Should the line above be "page_head = compound_head(page);" or >> am I missing something? > > page_head = page is there because if this is not a tail page it's also > the page_head. Only in case this is a tail page, compound_head is > called, otherwise it's guaranteed unnecessary. And if it's a tail page > compound_head has to run atomically inside irq disabled section > __get_user_pages_fast before returning. Otherwise ->first_page won't > be a stable pointer. Ahh, I see it now. Acked-by: Rik van Riel -- All rights reversed. -- 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