Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760837AbXJLRpn (ORCPT ); Fri, 12 Oct 2007 13:45:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757424AbXJLRpg (ORCPT ); Fri, 12 Oct 2007 13:45:36 -0400 Received: from elvis.mu.org ([192.203.228.196]:58824 "EHLO elvis.mu.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756244AbXJLRpf (ORCPT ); Fri, 12 Oct 2007 13:45:35 -0400 In-Reply-To: <1192201105.27435.41.camel@twins> References: <11854939641916-git-send-email-ssouhlal@FreeBSD.org> <200710120257.05960.nickpiggin@yahoo.com.au> <1192185439.27435.19.camel@twins> <200710120414.11026.nickpiggin@yahoo.com.au> <1192186222.27435.22.camel@twins> <20071012075317.591212ef@laptopd505.fenrus.org> <1192201105.27435.41.camel@twins> Mime-Version: 1.0 (Apple Message framework v752.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Cc: Arjan van de Ven , Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, Suleiman Souhlal , linux-mm , hugh Content-Transfer-Encoding: 7bit From: Suleiman Souhlal Subject: Re: [PATCH] mm: avoid dirtying shared mappings on mlock Date: Fri, 12 Oct 2007 10:45:17 -0700 To: Peter Zijlstra X-Mailer: Apple Mail (2.752.3) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 41 On Oct 12, 2007, at 7:58 AM, Peter Zijlstra wrote: > On Fri, 2007-10-12 at 07:53 -0700, Arjan van de Ven wrote: >> On Fri, 12 Oct 2007 12:50:22 +0200 >>>>> The pages will still be read-only due to dirty tracking, so the >>>>> first write will still do page_mkwrite(). >>>> >>>> Which can SIGBUS, no? >>> >>> Sure, but that is no different than any other mmap'ed write. I'm not >>> seeing how an mlocked region is special here. >>> >>> I agree it would be nice if mmap'ed writes would have better error >>> reporting than SIGBUS, but such is life. >> >> well... there's another consideration >> people use mlock() in cases where they don't want to go to the >> filesystem for paging and stuff as well (think the various iscsi >> daemons and other things that get in trouble).. those kind of uses >> really use mlock to avoid >> 1) IO to the filesystem >> 2) Needing memory allocations for pagefault like things >> at least for the more "hidden" cases... >> >> prefaulting everything ready pretty much gives them that... letting >> things fault on demand... nicely breaks that. > > Non of that is changed. So I'm a little puzzled as to which side you > argue. I think this might change the behavior in case you mlock sparse files. I guess currently the holes disappear when you mlock them, but with the patch the blocks wouldn't get allocated until they get written to. -- Suleiman - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/