From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4054DECE58C for ; Fri, 11 Oct 2019 09:49:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2200720659 for ; Fri, 11 Oct 2019 09:49:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727706AbfJKJtb (ORCPT ); Fri, 11 Oct 2019 05:49:31 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:56409 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726585AbfJKJtb (ORCPT ); Fri, 11 Oct 2019 05:49:31 -0400 Received: from 79.184.255.36.ipv4.supernova.orange.pl (79.184.255.36) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.292) id 1b220ecebb2d0121; Fri, 11 Oct 2019 11:49:29 +0200 From: "Rafael J. Wysocki" To: Andy Whitcroft Cc: linux-pm@vger.kernel.org, Len Brown , Pavel Machek , Andrea Righi , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] PM / hibernate: memory_bm_find_bit -- tighten node optimisation Date: Fri, 11 Oct 2019 11:49:29 +0200 Message-ID: <2167643.HFCj9E3NaD@kreacher> In-Reply-To: <20190925143912.22593-1-apw@canonical.com> References: <20190925143912.22593-1-apw@canonical.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, September 25, 2019 4:39:12 PM CEST Andy Whitcroft wrote: > When looking for a bit by number we make use of the cached result from the > preceding lookup to speed up operation. Firstly we check if the requested > pfn is within the cached zone and if not lookup the new zone. We then > check if the offset for that pfn falls within the existing cached node. > This happens regardless of whether the node is within the zone we are > now scanning. With certain memory layouts it is possible for this to > false trigger creating a temporary alias for the pfn to a different bit. > This leads the hibernation code to free memory which it was never allocated > with the expected fallout. > > Ensure the zone we are scanning matches the cached zone before considering > the cached node. > > Deep thanks go to Andrea for many, many, many hours of hacking and testing > that went into cornering this bug. > > Reported-by: Andrea Righi > Tested-by: Andrea Righi > Signed-off-by: Andy Whitcroft > --- > kernel/power/snapshot.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c > index 83105874f255..26b9168321e7 100644 > --- a/kernel/power/snapshot.c > +++ b/kernel/power/snapshot.c > @@ -734,8 +734,15 @@ static int memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn, > * We have found the zone. Now walk the radix tree to find the leaf node > * for our PFN. > */ > + > + /* > + * If the zone we wish to scan is the the current zone and the > + * pfn falls into the current node then we do not need to walk > + * the tree. > + */ > node = bm->cur.node; > - if (((pfn - zone->start_pfn) & ~BM_BLOCK_MASK) == bm->cur.node_pfn) > + if (zone == bm->cur.zone && > + ((pfn - zone->start_pfn) & ~BM_BLOCK_MASK) == bm->cur.node_pfn) > goto node_found; > > node = zone->rtree; > Applying as 5.5 material, thanks!