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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 0F56DC49ED7 for ; Mon, 16 Sep 2019 08:50:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCE24206C2 for ; Mon, 16 Sep 2019 08:50:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731329AbfIPIuh (ORCPT ); Mon, 16 Sep 2019 04:50:37 -0400 Received: from foss.arm.com ([217.140.110.172]:42062 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727387AbfIPIug (ORCPT ); Mon, 16 Sep 2019 04:50:36 -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 2AE8E1000; Mon, 16 Sep 2019 01:50:36 -0700 (PDT) Received: from [10.162.43.143] (p8cg001049571a15.blr.arm.com [10.162.43.143]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AC6BE3F59C; Mon, 16 Sep 2019 01:50:33 -0700 (PDT) Subject: Re: [PATCH] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() To: Mike Rapoport Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Oscar Salvador , Michal Hocko , David Hildenbrand , Pavel Tatashin , Dan Williams References: <1568612857-10395-1-git-send-email-anshuman.khandual@arm.com> <20190916063612.GA1502@linux.ibm.com> From: Anshuman Khandual Message-ID: <987dfde7-53f9-b013-5841-2c27c03d62d6@arm.com> Date: Mon, 16 Sep 2019 14:20:47 +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: <20190916063612.GA1502@linux.ibm.com> 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 09/16/2019 12:06 PM, Mike Rapoport wrote: > On Mon, Sep 16, 2019 at 11:17:37AM +0530, Anshuman Khandual wrote: >> In add_memory_resource() the memory range to be hot added first gets into >> the memblock via memblock_add() before arch_add_memory() is called on it. >> Reverse sequence should be followed during memory hot removal which already >> is being followed in add_memory_resource() error path. This now ensures >> required re-order between memblock_[free|remove]() and arch_remove_memory() >> during memory hot-remove. >> >> Cc: Andrew Morton >> Cc: Oscar Salvador >> Cc: Michal Hocko >> Cc: David Hildenbrand >> Cc: Pavel Tatashin >> Cc: Dan Williams >> Signed-off-by: Anshuman Khandual >> --- >> Original patch https://lkml.org/lkml/2019/9/3/327 >> >> Memory hot remove now works on arm64 without this because a recent commit >> 60bb462fc7ad ("drivers/base/node.c: simplify unregister_memory_block_under_nodes()"). >> >> David mentioned that re-ordering should still make sense for consistency >> purpose (removing stuff in the reverse order they were added). This patch >> is now detached from arm64 hot-remove series. >> >> https://lkml.org/lkml/2019/9/3/326 >> >> mm/memory_hotplug.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index c73f09913165..355c466e0621 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -1770,13 +1770,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) >> >> /* remove memmap entry */ >> firmware_map_remove(start, start + size, "System RAM"); >> - memblock_free(start, size); >> - memblock_remove(start, size); >> >> /* remove memory block devices before removing memory */ >> remove_memory_block_devices(start, size); >> >> arch_remove_memory(nid, start, size, NULL); >> + memblock_free(start, size); > > I don't see memblock_reserve() anywhere in memory_hotplug.c, so the > memblock_free() call here seems superfluous. I think it can be simply > dropped. I had observed that previously but was not sure whether or not there are still scenarios where it might be true. Error path in add_memory_resource() even just calls memblock_remove() not memblock_free(). Unless there is any objection, can just drop it.