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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_NEOMUTT 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 B5592C282C4 for ; Thu, 7 Feb 2019 13:36:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83050206DD for ; Thu, 7 Feb 2019 13:36:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727391AbfBGNga (ORCPT ); Thu, 7 Feb 2019 08:36:30 -0500 Received: from nat.nue.novell.com ([195.135.221.2]:56711 "EHLO suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727327AbfBGNg0 (ORCPT ); Thu, 7 Feb 2019 08:36:26 -0500 Received: by suse.de (Postfix, from userid 1000) id 8B21B41A4; Thu, 7 Feb 2019 14:36:24 +0100 (CET) Date: Thu, 7 Feb 2019 14:36:24 +0100 From: Oscar Salvador To: Robin Murphy Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, rafael@kernel.org, mhocko@kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH] mm/memory-hotplug: Add sysfs hot-remove trigger Message-ID: <20190207133620.a4vg2xqphsloke6i@d104.suse.de> References: <29ed519902512319bcc62e071d52b712fa97e306.1549469965.git.robin.murphy@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29ed519902512319bcc62e071d52b712fa97e306.1549469965.git.robin.murphy@arm.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 06, 2019 at 05:03:53PM +0000, Robin Murphy wrote: > ARCH_MEMORY_PROBE is a useful thing for testing and debugging hotplug, > but being able to exercise the (arguably trickier) hot-remove path would > be even more useful. Extend the feature to allow removal of offline > sections to be triggered manually to aid development. > > Signed-off-by: Robin Murphy > --- > > This is inspired by a previous proposal[1], but in coming up with a > more robust interface I ended up rewriting the whole thing from > scratch. The lack of documentation is semi-deliberate, since I don't > like the idea of anyone actually relying on this interface as ABI, but > as a handy tool it felt useful enough to be worth sharing :) Hi Robin, I think this might come in handy, especially when trying to test hot-remove on arch's that do not have any means to hot-remove memory, or even on virtual platforms that do not have yet support for hot-remove depending on the platform, like qemu/arm64. I could have used this while testing hot-remove on other archs for [1] > > Robin. > > [1] https://lore.kernel.org/lkml/22d34fe30df0fbacbfceeb47e20cb1184af73585.1511433386.git.ar@linux.vnet.ibm.com/ > > + if (mem->state != MEM_OFFLINE) > + return -EBUSY; We do have the helper "is_memblock_offlined()", although it is only used in one place now. So, I would rather use it here as well. > + > + ret = lock_device_hotplug_sysfs(); > + if (ret) > + return ret; > + > + if (device_remove_file_self(dev, attr)) { > + __remove_memory(pfn_to_nid(start_pfn), PFN_PHYS(start_pfn), > + MIN_MEMORY_BLOCK_SIZE * sections_per_block); Sorry, I am not into sysfs inners, but I thought that: device_del::device_remove_attrs::device_remove_groups::sysfs_remove_groups would be enough to remove the dev attributes. I guess in this case that is not enough, could you explain why? [1] https://patchwork.kernel.org/patch/10775339/ -- Oscar Salvador SUSE L3