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=-5.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 8327AC433E1 for ; Fri, 24 Jul 2020 03:14:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 444AA22CAF for ; Fri, 24 Jul 2020 03:14:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="HlRbJgYK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 444AA22CAF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DC9306B002F; Thu, 23 Jul 2020 23:14:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D54C26B0030; Thu, 23 Jul 2020 23:14:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C438F8D0007; Thu, 23 Jul 2020 23:14:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0248.hostedemail.com [216.40.44.248]) by kanga.kvack.org (Postfix) with ESMTP id ABAB96B002F for ; Thu, 23 Jul 2020 23:14:07 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 25A581524B for ; Fri, 24 Jul 2020 03:14:07 +0000 (UTC) X-FDA: 77071500534.07.mark64_0004ec126f44 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 05AB318075DB9 for ; Fri, 24 Jul 2020 03:14:06 +0000 (UTC) X-HE-Tag: mark64_0004ec126f44 X-Filterd-Recvd-Size: 4284 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Fri, 24 Jul 2020 03:14:06 +0000 (UTC) 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 X-Rspamd-Queue-Id: 05AB318075DB9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 Content-Transfer-Encoding: quoted-printable 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 Fri, 24 Jul 2020 12:04:02 +0900 Joonsoo Kim wrote: > 2020=EB=85=84 7=EC=9B=94 24=EC=9D=BC (=EA=B8=88) =EC=98=A4=EC=A0=84 11:= 36, Andrew Morton =EB=8B=98=EC=9D=B4 =EC=9E=91= =EC=84=B1: > > > > On Fri, 24 Jul 2020 11:23:52 +0900 Joonsoo Kim wro= te: > > > > > > > Second, clearing __GFP_MOVABLE in current_gfp_context() has a s= ide 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 effect= s 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 f= allback would > > > cover the problematic case. It's mentioned in the commit descriptio= n. Perhap, > > > performance would be improved due to reduced retry and more availab= le memory > > > (we can use ZONE_MOVABLE with this patch) but it would be neglectab= le. > > > > > > > d7fefcc8de9147c is over a year old. Why did we only just discove= r > > > > this? This makes one wonder how serious those end-user-visible e= ffects > > > > 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) >=20 > Thanks for the pointer! >=20 > Hmm... I'm not sure the correct way to handle this patch. I thought tha= t > memalloc_nocma_{save,restore} is an API that is callable from the modul= e. > 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 caus= e > a problem. But, yes, there is no visible problem to the end-user, at le= ast, > within the mainline so it is possibly not a stable candidate. >=20 > 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.