Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758110Ab2FFTLG (ORCPT ); Wed, 6 Jun 2012 15:11:06 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:40099 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753987Ab2FFTLC (ORCPT ); Wed, 6 Jun 2012 15:11:02 -0400 Message-ID: <4FCFAB3D.6080000@gmail.com> Date: Wed, 06 Jun 2012 15:10:53 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Andrew Morton CC: Linus Torvalds , KOSAKI Motohiro , david@lang.hm, Christoph Lameter , Andi Kleen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Dave Jones , Mel Gorman , stable@vger.kernel.org, hughd@google.com, sivanich@sgi.com Subject: Re: [PATCH 0/6] mempolicy memory corruption fixlet References: <1338368529-21784-1-git-send-email-kosaki.motohiro@gmail.com> <20120530184638.GU27374@one.firstfloor.org> <20120530193234.GV27374@one.firstfloor.org> <20120530201042.GY27374@one.firstfloor.org> <20120605121711.bb392118.akpm@linux-foundation.org> In-Reply-To: <20120605121711.bb392118.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2305 Lines: 59 (6/5/12 3:17 PM), Andrew Morton wrote: > On Tue, 5 Jun 2012 12:02:25 -0700 > Linus Torvalds wrote: > >> I'm coming back to this email thread, because I didn't apply the >> series due to all the ongoing discussion and hoping that somebody >> would put changelog fixes and ack notices etc together. >> >> I'd also really like to know that the people who saw the problem that >> caused the current single patch (that this series reverts) would test >> the whole series. Maybe that happened and I didn't notice it in the >> threads, but I don't think so. I'm not surprised this. If many people are interesting to review this area, mempolicy wouldn't have break so a lot. >> In fact, right now I'm assuming that the series will eventually come >> to me through Andrew. Andrew, correct? > > yup. > > I expect there will be a v2 series (at least). It's unclear what > we'll be doing with [2/6]: whether the patch will be reworked, or > whether Andi misunderstood its effects? Maybe because Andi didn't join bug fix works in this area for several years? Currently, mbind(2) is completely broken. A primary role of mbind(2) is to update memory policy of some vmas and Mel's fix remvoed it. Then, mbind is almostly no-op. it's a regression. I'm not clear which point you seems unclear. So, let's repeat a description of [2/6]. There are two problem now, alloc_pages_vma() has strong and wrong assumption. vma->policy never have MPOL_F_SHARED and shared_policy->policy must have it. And, cpusets rebinding ignore mpol->refcnt and updates it forcibly. The final point is to implement cow. But for it, we need rewrite mpol->rebind family completely. It doesn't fit for 3.5 timeframe. The downside of patch [2/6] is very small. because, A memplicy is only shared three cases, 1) mbind() updates multiple vmas 2) mbind() updates shmem vma 3) A shared policy splits into two regions by a part region update. All of them are rare. Because nobody hit kernel panic until now. Then I don't think my patch increase memory footprint. -- 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/