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 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 127FCC46460 for ; Tue, 14 Aug 2018 10:09:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE26B21733 for ; Tue, 14 Aug 2018 10:09:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE26B21733 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732087AbeHNMzs (ORCPT ); Tue, 14 Aug 2018 08:55:48 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40970 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731082AbeHNMzs (ORCPT ); Tue, 14 Aug 2018 08:55:48 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B5FF040241CF; Tue, 14 Aug 2018 10:09:17 +0000 (UTC) Received: from [10.36.117.57] (ovpn-117-57.ams2.redhat.com [10.36.117.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 39DC72156712; Tue, 14 Aug 2018 10:09:15 +0000 (UTC) Subject: Re: [PATCH v2 2/3] mm/memory_hotplug: Drop mem_blk check from unregister_mem_sect_under_nodes To: Oscar Salvador Cc: akpm@linux-foundation.org, mhocko@suse.com, dan.j.williams@intel.com, jglisse@redhat.com, rafael@kernel.org, yasu.isimatu@gmail.com, logang@deltatee.com, dave.jiang@intel.com, Jonathan.Cameron@huawei.com, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador References: <20180813154639.19454-1-osalvador@techadventures.net> <20180813154639.19454-3-osalvador@techadventures.net> <82148bc6-672d-6610-757f-d910a17d23c6@redhat.com> <20180814093652.GA6878@techadventures.net> <39454952-f8c9-4ded-acb5-02192e889de0@redhat.com> <20180814100644.GB6979@techadventures.net> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180814100644.GB6979@techadventures.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 14 Aug 2018 10:09:17 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 14 Aug 2018 10:09:17 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'david@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.08.2018 12:06, Oscar Salvador wrote: > On Tue, Aug 14, 2018 at 11:44:50AM +0200, David Hildenbrand wrote: >> >> Yes I know, as I said, if it would be local to a file I would not care. >> Making this functions never return an error is nice, though (and as you >> noted, the return value is never checked). >> >> I am a friend of stating which conditions a function expects to hold if >> a function can be called from other parts of the system. Usually I >> prefer to use BUG_ONs for that (whoever decides to call it can directly >> see what he as to check before calling) or comments. But comments tend >> to become obsolete. > > Uhm, I think a BUG_ON is too much here. > We could replace the check with a WARN_ON, just in case > a new function decides to call unregister_mem_sect_under_nodes() in the future. > > Something like: > > WARN_ON(!mem_blk) > return; > > In that case, we should get a nice splat in the logs that should tell us > who is calling it with an invalid mem_blk. > Whatever you think is best. I have no idea what the general rules in MM code are. Maybe dropping this check is totally fine. -- Thanks, David / dhildenb