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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 BABCBC432C1 for ; Tue, 24 Sep 2019 08:41:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C454214AF for ; Tue, 24 Sep 2019 08:41:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440679AbfIXIlC (ORCPT ); Tue, 24 Sep 2019 04:41:02 -0400 Received: from foss.arm.com ([217.140.110.172]:55808 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439012AbfIXIlC (ORCPT ); Tue, 24 Sep 2019 04:41:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB404142F; Tue, 24 Sep 2019 01:41:01 -0700 (PDT) Received: from [10.162.40.141] (p8cg001049571a15.blr.arm.com [10.162.40.141]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 789293F59C; Tue, 24 Sep 2019 01:40:55 -0700 (PDT) Subject: Re: [PATCH V8 2/2] arm64/mm: Enable memory hot remove To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, mhocko@suse.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com, steve.capper@arm.com, broonie@kernel.org, valentin.schneider@arm.com, Robin.Murphy@arm.com, steven.price@arm.com, suzuki.poulose@arm.com, ira.weiny@intel.com References: <1569217425-23777-1-git-send-email-anshuman.khandual@arm.com> <1569217425-23777-3-git-send-email-anshuman.khandual@arm.com> <20190923111745.GG15392@bombadil.infradead.org> From: Anshuman Khandual Message-ID: <962f7849-f42d-9154-92ae-3125d2f19504@arm.com> Date: Tue, 24 Sep 2019 14:11:12 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190923111745.GG15392@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/23/2019 04:47 PM, Matthew Wilcox wrote: > On Mon, Sep 23, 2019 at 11:13:45AM +0530, Anshuman Khandual wrote: >> +#ifdef CONFIG_MEMORY_HOTPLUG >> +static void free_hotplug_page_range(struct page *page, size_t size) >> +{ >> + WARN_ON(!page || PageReserved(page)); > > WARN_ON(!page) isn't terribly useful. You're going to crash on the very > next line when you call page_address() anyway. If this line were > > if (WARN_ON(!page || PageReserved(page))) > return; > > it would make sense, or if it were just > > WARN_ON(PageReserved(page)) > > it would also make sense. I guess WARN_ON(PageReserved(page)) should be good enough to make sure that page being freed here was originally allocated at runtime for a previous memory hot add operation and did not some how come from the memblock reserved area. That was the original objective for this check. Will change it. > >> + free_pages((unsigned long)page_address(page), get_order(size)); >> +} >