From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161076AbWGID0K (ORCPT ); Sat, 8 Jul 2006 23:26:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161075AbWGID0K (ORCPT ); Sat, 8 Jul 2006 23:26:10 -0400 Received: from smtp107.mail.mud.yahoo.com ([209.191.85.217]:12479 "HELO smtp107.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S964923AbWGID0J (ORCPT ); Sat, 8 Jul 2006 23:26:09 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=ekdqOSNki1K8wDxrHwzYkzPj1nR58YQCr9mWxmDAQ+c0m+o6KZJXhZGppo+LiL2ExsMRXpIKBYt/Ti6/cp3dOmuoT1ajQQApX2nlg6Hl6XZH8kxU7mItvD/ZG1FkJAi1sBDosSsiZtahBolIoKcCuHkp1K6RsPsVX3Z/znEp3VY= ; Message-ID: <44B0774E.5010103@yahoo.com.au> Date: Sun, 09 Jul 2006 13:26:06 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Marc Singer CC: Linux-Kernel Subject: Re: DMA memory, split_page, BUG_ON(PageCompound()), sound References: <20060709000703.GA9806@cerise.buici.com> In-Reply-To: <20060709000703.GA9806@cerise.buici.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Marc Singer wrote: > I'm investigating why I am triggering a BUG_ON in split_page() when I > use the sound subsystems dma memory allocation aide. > > The crux of the problem appears to be that snd_malloc_dev_pages() > passes __GFP_COMP into dma_alloc_coherent(). On the ARM and several > other architectures, the dma allocation code calls split_page () with > pages allocated with this flag which, in turn, triggers the BUG_ON() > check for the CompoundPage flag. > > So, the questions are these: Who is doing the wrong thing? Should the > snd_malloc_dev_pages() call drop the __GFP_COMP flag? Should > split_page() allow the page to be compound? Should __GFP_COMP be 0 on > ARM and other architectures that don't support compound pages? I personally never liked the explicit __GFP_COMP going in everywhere, and would have much preferred a GFP_USERMAP, which the architecture / allocator could satisfy as they liked. As a hack, you can make arm's dma_alloc_coherent() drop __GFP_COMP, which should work. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com