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=-5.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 2CAB6C433DF for ; Fri, 24 Jul 2020 03:14:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A8F1207FC for ; Fri, 24 Jul 2020 03:14:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595560448; bh=7Nn2vijdOpJYv5RRp0kMLo2D//KQ22IaqcB8VQUTtz4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=cIwp6WyeA/vEoLBPwCIrVEG0SEZC8U7vEK0jKgvws/XymCCWpcMvpMZH4P0j9auDC KQPRRUn0gjxE6MeZr+ncHkczITiGT8IYfPtkh4ZG/qCLa1C0YVffDc92N7orYwaOC7 wmixCcVdPFAXY0s1XzSuQJB20zU4VbKbilT48Zds= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726760AbgGXDOH (ORCPT ); Thu, 23 Jul 2020 23:14:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:43408 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726178AbgGXDOG (ORCPT ); Thu, 23 Jul 2020 23:14:06 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 0DDF220792; Fri, 24 Jul 2020 03:14:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595560445; bh=7Nn2vijdOpJYv5RRp0kMLo2D//KQ22IaqcB8VQUTtz4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HlRbJgYKPEVZSsXegUjp/2v7/SwgSpMQYylFMhoicS2JzBa03usl8BoFyGcmB0z7B n1RyZpC+bJY2hnWvW8bJMa6OVOAmq5NvlrrjyOpBEEthdHyI0RlDSmPeTj65hZZO8B AcF2dBRPplDmW6/IEOxvQzpgoKWBdUIrGGEFs5xo= Date: Thu, 23 Jul 2020 20:14:04 -0700 From: Andrew Morton To: Joonsoo Kim Cc: Linux Memory Management List , LKML , kernel-team@lge.com, Vlastimil Babka , Christoph Hellwig , Roman Gushchin , Mike Kravetz , Naoya Horiguchi , Michal Hocko , "Aneesh Kumar K . V" , Joonsoo Kim , stable@vger.kernel.org Subject: Re: [PATCH v2] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs Message-Id: <20200723201404.f76ccd792c9e74f3ae8ec9f5@linux-foundation.org> In-Reply-To: References: <1595468942-29687-1-git-send-email-iamjoonsoo.kim@lge.com> <20200723180814.acde28b92ce6adc785a79120@linux-foundation.org> <20200723193600.28e3eedd00925b22f7ca9780@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 24 Jul 2020 12:04:02 +0900 Joonsoo Kim wrote: > 2020년 7월 24일 (금) 오전 11:36, Andrew Morton 님이 작성: > > > > On Fri, 24 Jul 2020 11:23:52 +0900 Joonsoo Kim wrote: > > > > > > > Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect > > > > > to exclude the memory on the ZONE_MOVABLE for allocation target. > > > > > > > > More whoops. > > > > > > > > Could we please have a description of the end-user-visible effects of > > > > this change? Very much needed when proposing a -stable backport, I think. > > > > > > In fact, there is no noticeable end-user-visible effect since the fallback would > > > cover the problematic case. It's mentioned in the commit description. Perhap, > > > performance would be improved due to reduced retry and more available memory > > > (we can use ZONE_MOVABLE with this patch) but it would be neglectable. > > > > > > > d7fefcc8de9147c is over a year old. Why did we only just discover > > > > this? This makes one wonder how serious those end-user-visible effects > > > > are? > > > > > > As mentioned above, there is no visible problem to the end-user. > > > > OK, thanks. In that case, I don't believe that a stable backport is > > appropriate? > > > > (Documentation/process/stable-kernel-rules.rst) > > Thanks for the pointer! > > Hmm... I'm not sure the correct way to handle this patch. I thought that > memalloc_nocma_{save,restore} is an API that is callable from the module. > If it is true, it's better to regard this patch as the stable candidate since > out-of-tree modules could use it without the fallback and it would cause > a problem. But, yes, there is no visible problem to the end-user, at least, > within the mainline so it is possibly not a stable candidate. > > Please share your opinion about this situation. We tend not to care much about out-of-tree modules. I don't think a theoretical concern for out-of-tree code justifies risking the stability of -stable kernels.