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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 AB340C43331 for ; Mon, 11 Nov 2019 13:28:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 770062196E for ; Mon, 11 Nov 2019 13:28:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573478896; bh=dfnaxHz6D/4QYLWkG0Tk300Aydr7Uwv3T4hLGud9mLM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=c2WBNAmyL6yDN6xFV0tZo8c81Cc9xrQZzTmK2ZB1w56QlrHvPMrP+BSJLBgIUHAcI 3vqfWHuRQ1bJ1/fOorLo51b3jTbq3IeeXhMo4eDIde+uVv64m1ro6qgRoPZqsRoEi/ Ix/WLReuGCF4IAAjF8JIoYQAX9H/zhQCXSIKObDo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727032AbfKKN2P (ORCPT ); Mon, 11 Nov 2019 08:28:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:51762 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726910AbfKKN2P (ORCPT ); Mon, 11 Nov 2019 08:28:15 -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 52D3FAD00; Mon, 11 Nov 2019 13:28:13 +0000 (UTC) Date: Mon, 11 Nov 2019 14:28:12 +0100 From: Michal Hocko To: Chris Down Cc: Qian Cai , akpm@linux-foundation.org, hannes@cmpxchg.org, guro@fb.com, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next] mm/vmscan: fix an undefined behavior for zone id Message-ID: <20191111132812.GK1396@dhcp22.suse.cz> References: <20191108204407.1435-1-cai@lca.pw> <64E60F6F-7582-427B-8DD5-EF97B1656F5A@lca.pw> <20191111130516.GA891635@chrisdown.name> <20191111131427.GB891635@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191111131427.GB891635@chrisdown.name> 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 Mon 11-11-19 13:14:27, Chris Down wrote: > Chris Down writes: > > Ah, I just saw this in my local checkout and thought it was from my > > changes, until I saw it's also on clean mmots checkout. Thanks for the > > fixup! > > Also, does this mean we should change callers that may pass through > zone_idx=MAX_NR_ZONES to become MAX_NR_ZONES-1 in a separate commit, then > remove this interim fixup? I'm worried otherwise we might paper over real > issues in future. Yes, removing this special casing is reasonable. I am not sure MAX_NR_ZONES - 1 is a better choice though. It is error prone and zone_idx is the highest zone we should consider and MAX_NR_ZONES - 1 be ZONE_DEVICE if it is configured. But ZONE_DEVICE is really standing outside of MM reclaim code AFAIK. It would be probably better to have MAX_LRU_ZONE (equal to MOVABLE) and use it instead. -- Michal Hocko SUSE Labs