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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E33D8C433E2 for ; Wed, 9 Sep 2020 12:36:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 70D0421D40 for ; Wed, 9 Sep 2020 12:36:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="C19O5ED9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 70D0421D40 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E31418E0005; Wed, 9 Sep 2020 08:36:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DE1198E0001; Wed, 9 Sep 2020 08:36:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CF7D58E0005; Wed, 9 Sep 2020 08:36:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0183.hostedemail.com [216.40.44.183]) by kanga.kvack.org (Postfix) with ESMTP id B75588E0001 for ; Wed, 9 Sep 2020 08:36:29 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 77E6D180AD811 for ; Wed, 9 Sep 2020 12:36:29 +0000 (UTC) X-FDA: 77243471298.03.mass80_0e14c3a270dd Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 45AD228A4E8 for ; Wed, 9 Sep 2020 12:36:29 +0000 (UTC) X-HE-Tag: mass80_0e14c3a270dd X-Filterd-Recvd-Size: 3680 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Sep 2020 12:36:28 +0000 (UTC) Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 40C8421941; Wed, 9 Sep 2020 12:36:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599654987; bh=MyTxeMGJ0aUch6xrrUFEzK1mWKVG/hL4CJaX7/Slcb4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=C19O5ED9pwEGaBq3WjWQS4SEZ5Lwz/9O2+IjIPFpWqNr+we1f2lRLe54jer5JqlNM 0eSNjuQLOcEhFYhT4ftwMDXBld7PGwh/f/JVfvv+XZE6TQig928vZxQqqZDRZPZQsc zPOFUH1l4t7YyS3kNcaMlIRHQgbQ9Wd+oQufliok= Date: Wed, 9 Sep 2020 14:36:37 +0200 From: Greg Kroah-Hartman To: David Hildenbrand Cc: Laurent Dufour , Michal Hocko , akpm@linux-foundation.org, Oscar Salvador , rafael@kernel.org, nathanl@linux.ibm.com, cheloha@linux.ibm.com, stable@vger.kernel.org, linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm: don't rely on system state to detect hot-plug operations Message-ID: <20200909123637.GA671204@kroah.com> References: <5cbd92e1-c00a-4253-0119-c872bfa0f2bc@redhat.com> <20200908170835.85440-1-ldufour@linux.ibm.com> <20200909074011.GD7348@dhcp22.suse.cz> <9faac1ce-c02d-7dbc-f79a-4aaaa5a73d28@linux.ibm.com> <20200909090953.GE7348@dhcp22.suse.cz> <4cdb54be-1a92-4ba4-6fee-3b415f3468a9@linux.ibm.com> <9ad553f2-ebbf-cae5-5570-f60d2c965c41@redhat.com> <20200909123001.GA670250@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 45AD228A4E8 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 09, 2020 at 02:32:57PM +0200, David Hildenbrand wrote: > On 09.09.20 14:30, Greg Kroah-Hartman wrote: > > On Wed, Sep 09, 2020 at 11:24:24AM +0200, David Hildenbrand wrote: > >>>> I am not sure an enum is going to make the existing situation less > >>>> messy. Sure we somehow have to distinguish boot init and runtime hotplug > >>>> because they have different constrains. I am arguing that a) we should > >>>> have a consistent way to check for those and b) we shouldn't blow up > >>>> easily just because sysfs infrastructure has failed to initialize. > >>> > >>> For the point a, using the enum allows to know in register_mem_sect_under_node() > >>> if the link operation is due to a hotplug operation or done at boot time. > >>> > >>> For the point b, one option would be ignore the link error in the case the link > >>> is already existing, but that BUG_ON() had the benefit to highlight the root issue. > >>> > >> > >> WARN_ON_ONCE() would be preferred - not crash the system but still > >> highlight the issue. > > > > Many many systems now run with 'panic on warn' enabled, so that wouldn't > > change much :( > > > > If you can warn, you can properly just print an error message and > > recover from the problem. > > Maybe VM_WARN_ON_ONCE() then to detect this during testing? If you all use that, sure. > (we basically turned WARN_ON_ONCE() useless with 'panic on warn' getting > used in production - behaves like BUG_ON and BUG_ON is frowned upon) Yes we have, but in the end, it's good, those things should be fixed and not accessable by anything a user can trigger. thanks, greg k-h