From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263493AbUDBBJY (ORCPT ); Thu, 1 Apr 2004 20:09:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263480AbUDBBJX (ORCPT ); Thu, 1 Apr 2004 20:09:23 -0500 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:64402 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S263493AbUDBBJA (ORCPT ); Thu, 1 Apr 2004 20:09:00 -0500 Date: Fri, 2 Apr 2004 03:09:00 +0200 From: Andrea Arcangeli To: Andrew Morton Cc: pavel@suse.cz, linux-kernel@vger.kernel.org, hugh@veritas.com Subject: Re: Properly stop kernel threads on aic7xxx Message-ID: <20040402010900.GJ18585@dualathlon.random> References: <20040401170808.GA696@elf.ucw.cz> <20040402003520.GH18585@dualathlon.random> <20040401170403.76d86432.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040401170403.76d86432.akpm@osdl.org> User-Agent: Mutt/1.4.1i X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 01, 2004 at 05:04:03PM -0800, Andrew Morton wrote: > 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. we do the same in bigpages 2.4 just fine with a basic math on the page_t knowing it's 2M naturally aligned, very easy to find the head page on vmas with VM_HUGETLBFS. > 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. currently it's turned on only with HUGTLBFS=y though.