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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 E2766C43387 for ; Wed, 9 Jan 2019 18:56:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8BC820859 for ; Wed, 9 Jan 2019 18:56:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727971AbfAIS4y (ORCPT ); Wed, 9 Jan 2019 13:56:54 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:42930 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727641AbfAIS4y (ORCPT ); Wed, 9 Jan 2019 13:56:54 -0500 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 707F6C79; Wed, 9 Jan 2019 18:56:53 +0000 (UTC) Date: Wed, 9 Jan 2019 10:56:52 -0800 From: Andrew Morton To: Arun KS Cc: Michal Hocko , Alexander Duyck , arunks.linux@gmail.com, vbabka@suse.cz, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, getarunks@gmail.com Subject: Re: [PATCH v7] mm/page_alloc.c: memory_hotplug: free pages as higher order Message-Id: <20190109105652.40e24fa969a2bb7a58e097a8@linux-foundation.org> In-Reply-To: <2efb06e91d9af48bf3d1d38bd50e0458@codeaurora.org> References: <1546578076-31716-1-git-send-email-arunks@codeaurora.org> <20190108181352.GI31793@dhcp22.suse.cz> <20190109073718.GM31793@dhcp22.suse.cz> <20190109084031.GN31793@dhcp22.suse.cz> <20190109105754.GR31793@dhcp22.suse.cz> <2efb06e91d9af48bf3d1d38bd50e0458@codeaurora.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 09 Jan 2019 16:36:36 +0530 Arun KS wrote: > On 2019-01-09 16:27, Michal Hocko wrote: > > On Wed 09-01-19 16:12:48, Arun KS wrote: > > [...] > >> It will be called once per online of a section and the arg value is > >> always > >> set to 0 while entering online_pages_range. > > > > You rare right that this will be the case in the most simple scenario. > > But the point is that the callback can be called several times from > > walk_system_ram_range and then your current code wouldn't work > > properly. > > Thanks. Will use += The v8 patch https://lore.kernel.org/lkml/1547032395-24582-1-git-send-email-arunks@codeaurora.org/T/#u (which you apparently sent 7 minutes after typing the above) still has static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, void *arg) { - unsigned long i; unsigned long onlined_pages = *(unsigned long *)arg; - struct page *page; if (PageReserved(pfn_to_page(start_pfn))) - for (i = 0; i < nr_pages; i++) { - page = pfn_to_page(start_pfn + i); - (*online_page_callback)(page); - onlined_pages++; - } + onlined_pages = online_pages_blocks(start_pfn, nr_pages); Even then the code makes no sense. static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, void *arg) { unsigned long onlined_pages = *(unsigned long *)arg; if (PageReserved(pfn_to_page(start_pfn))) onlined_pages += online_pages_blocks(start_pfn, nr_pages); online_mem_sections(start_pfn, start_pfn + nr_pages); *(unsigned long *)arg += onlined_pages; return 0; } Either the final assignment should be *(unsigned long *)arg = onlined_pages; or the initialization should be unsigned long onlined_pages = 0; This is becoming a tad tiresome and I'd prefer not to have to check up on such things. Can we please get this right?