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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5BFEC433F5 for ; Wed, 1 Dec 2021 03:00:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5E0826B0073; Tue, 30 Nov 2021 22:00:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 58EB56B0074; Tue, 30 Nov 2021 22:00:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4552D6B0075; Tue, 30 Nov 2021 22:00:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0025.hostedemail.com [216.40.44.25]) by kanga.kvack.org (Postfix) with ESMTP id 35C2F6B0073 for ; Tue, 30 Nov 2021 22:00:47 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id F0B1C8249980 for ; Wed, 1 Dec 2021 03:00:36 +0000 (UTC) X-FDA: 78867722514.10.BB965B1 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf25.hostedemail.com (Postfix) with ESMTP id C9E60B000187 for ; Wed, 1 Dec 2021 03:00:36 +0000 (UTC) Received: from mail.kernel.org (unknown [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 3E518CE1759; Wed, 1 Dec 2021 03:00:32 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2082B604DC; Wed, 1 Dec 2021 03:00:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1638327630; bh=rE92ZsrRFGUJPqC5lq6LvJdf/WnYGPPYf8ZNjb8IlQE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=hUVlO+IJ/5gv/YvH3nJknIPO20GcfN5Lyn7puPrkGgiCIFhvxLc1HyRaKCboxicCG oewbh1UifO7DWe1+HMRR49iZX2GheYjDxGlRiHhxAEuylG8/5hRP3NxhFTt9LmLReD Hyyxdp5tcC7Ko647SQoe5/ZCJ4FohwM3Ksy9FyPc= Date: Tue, 30 Nov 2021 19:00:28 -0800 From: Andrew Morton To: "Aneesh Kumar K.V" Cc: linux-mm@kvack.org, Ben Widawsky , Dave Hansen , Feng Tang , Michal Hocko , Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Andi Kleen , Dan Williams , Huang Ying , linux-api@vger.kernel.org Subject: Re: [PATCH v5 2/3] mm/mempolicy: add set_mempolicy_home_node syscall Message-Id: <20211130190028.6644054bc7142af36ef5c648@linux-foundation.org> In-Reply-To: <87wnkqaujt.fsf@linux.ibm.com> References: <20211116064238.727454-1-aneesh.kumar@linux.ibm.com> <20211116064238.727454-3-aneesh.kumar@linux.ibm.com> <20211129140215.11b7cf9f1034a7fe7017768c@linux-foundation.org> <87wnkqaujt.fsf@linux.ibm.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C9E60B000187 X-Stat-Signature: kf9s6dur6h3z6hgdkaf67g1tdgsprijo Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=hUVlO+IJ; dmarc=none; spf=pass (imf25.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-HE-Tag: 1638327636-335670 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 30 Nov 2021 14:29:02 +0530 "Aneesh Kumar K.V" wrote: > > What's the thinking here? The node can later be offlined and the > > kernel takes no action to reset home nodes, so why not permit setting a > > presently-offline node as the home node? Checking here seems rather > > arbitrary? > > The node online check was needed to avoid accessing > uninitialised pgdat structure. Such an access can result in > below crash Oh. This is unobvious from reading the code. Which calls for a comment, no?