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=-5.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 E73EBC43612 for ; Wed, 19 Dec 2018 10:20:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3A0E218AE for ; Wed, 19 Dec 2018 10:20:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545214819; bh=ttyVGbaKN7UlnKfxv94c4qCrFzxY9A4xv3HTQSoT5S4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=f+O/yygyw/85BYrogm+NIg6kc+jMgbR1OLKfhLbKMz6lACi+AF9BctBOv0qX5M5UV 4CfWQM/FzXWjvXlEKtCzNInh0QUi4dCDs3osIPey4Tw02qLE8nHKu2aHwrxeV8DKKW OJ4zEGBJHVCqUs7P2smvi0uaE2A/2J+1Vb/+pyrQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729001AbeLSKUP (ORCPT ); Wed, 19 Dec 2018 05:20:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:42582 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728570AbeLSKUN (ORCPT ); Wed, 19 Dec 2018 05:20:13 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5D610B038; Wed, 19 Dec 2018 10:20:11 +0000 (UTC) Date: Wed, 19 Dec 2018 11:20:10 +0100 From: Michal Hocko To: Qian Cai Cc: akpm@linux-foundation.org, mingo@kernel.org, hpa@zytor.com, mgorman@techsingularity.net, tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: skip checking poison pattern for page_to_nid() Message-ID: <20181219102010.GF5758@dhcp22.suse.cz> References: <1545172285.18411.26.camel@lca.pw> <20181219015732.26179-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181219015732.26179-1-cai@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 18-12-18 20:57:32, Qian Cai wrote: [...] > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 5411de93a363..f083f366ea90 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -985,9 +985,7 @@ extern int page_to_nid(const struct page *page); > #else > static inline int page_to_nid(const struct page *page) > { > - struct page *p = (struct page *)page; > - > - return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK; > + return (page->flags >> NODES_PGSHIFT) & NODES_MASK; > } > #endif I didn't get to think about a proper fix but this is clearly worng. If the page is still poisoned then flags are clearly bogus and the node you get is a garbage as well. Have you actually tested this patch? -- Michal Hocko SUSE Labs