From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263015AbUDBBB6 (ORCPT ); Thu, 1 Apr 2004 20:01:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263475AbUDBBB5 (ORCPT ); Thu, 1 Apr 2004 20:01:57 -0500 Received: from fw.osdl.org ([65.172.181.6]:11748 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S263015AbUDBBBy (ORCPT ); Thu, 1 Apr 2004 20:01:54 -0500 Date: Thu, 1 Apr 2004 17:04:03 -0800 From: Andrew Morton To: Andrea Arcangeli Cc: pavel@suse.cz, linux-kernel@vger.kernel.org, hugh@veritas.com Subject: Re: Properly stop kernel threads on aic7xxx Message-Id: <20040401170403.76d86432.akpm@osdl.org> In-Reply-To: <20040402003520.GH18585@dualathlon.random> References: <20040401170808.GA696@elf.ucw.cz> <20040402003520.GH18585@dualathlon.random> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrea Arcangeli wrote: > > I'm also unsure why _all_ multipage allocations really need this > compound thing setup and why can't the owner of the page take care of > the refcounting itself by always using the head page. I may actually > add a GFP bitflag asking for a multipage but w/o a compound setup. There > are million ways to fix this, none of which is obvious. For direct-io into higher-order pages. When doing direct-io into a hugetlb page we need to make sure that get_user_pages() pins the correct pageframe. Possibly we need to turn it on regardless of CONFIG_HUGETLBPAGE for people who want to do direct-io or PEEKTEXT/POKETEXT into mmapped soundcard buffers, for example. Perhaps there's a race which could permit direct-io to write to a freed page via this route.. Davem had some reason why he might want to turn on the compound logic permanently - related to TCP access to/from higher-order pages, I think.