From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:54292 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728004AbfGPIqk (ORCPT ); Tue, 16 Jul 2019 04:46:40 -0400 Date: Tue, 16 Jul 2019 10:46:34 +0200 From: Oscar Salvador Subject: Re: [PATCH v3 10/11] mm/memory_hotplug: Make unregister_memory_block_under_nodes() never fail Message-ID: <20190716084626.GA12394@linux> References: <20190527111152.16324-1-david@redhat.com> <20190527111152.16324-11-david@redhat.com> <20190701085144.GJ6376@dhcp22.suse.cz> <20190701093640.GA17349@linux> <20190701102756.GO6376@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-s390-owner@vger.kernel.org List-ID: To: David Hildenbrand Cc: Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, Dan Williams , Wei Yang , Igor Mammedov , Greg Kroah-Hartman , "Rafael J. Wysocki" , Alex Deucher , "David S. Miller" , Mark Brown , Chris Wilson , Jonathan Cameron On Mon, Jul 15, 2019 at 01:10:33PM +0200, David Hildenbrand wrote: > On 01.07.19 12:27, Michal Hocko wrote: > > On Mon 01-07-19 11:36:44, Oscar Salvador wrote: > >> On Mon, Jul 01, 2019 at 10:51:44AM +0200, Michal Hocko wrote: > >>> Yeah, we do not allow to offline multi zone (node) ranges so the current > >>> code seems to be over engineered. > >>> > >>> Anyway, I am wondering why do we have to strictly check for already > >>> removed nodes links. Is the sysfs code going to complain we we try to > >>> remove again? > >> > >> No, sysfs will silently "fail" if the symlink has already been removed. > >> At least that is what I saw last time I played with it. > >> > >> I guess the question is what if sysfs handling changes in the future > >> and starts dropping warnings when trying to remove a symlink is not there. > >> Maybe that is unlikely to happen? > > > > And maybe we handle it then rather than have a static allocation that > > everybody with hotremove configured has to pay for. > > > > So what's the suggestion? Dropping the nodemask_t completely and calling > sysfs_remove_link() on already potentially removed links? > > Of course, we can also just use mem_blk->nid and rest assured that it > will never be called for memory blocks belonging to multiple nodes. Hi David, While it is easy to construct a scenario where a memblock belongs to multiple nodes, I have to confess that I yet have not seen that in a real-world scenario. Given said that, I think that the less risky way is to just drop the nodemask_t and do not care about calling sysfs_remove_link() for already removed links. As I said, sysfs_remove_link() will silently fail when it fails to find the symlink, so I do not think it is a big deal. -- Oscar Salvador SUSE L3