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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 04393C433E3 for ; Fri, 24 Jul 2020 03:32:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9487120709 for ; Fri, 24 Jul 2020 03:32:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UA/Edbu+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9487120709 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EAC2E6B002E; Thu, 23 Jul 2020 23:32:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E36A98D0003; Thu, 23 Jul 2020 23:32:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD62E6B0030; Thu, 23 Jul 2020 23:32:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0145.hostedemail.com [216.40.44.145]) by kanga.kvack.org (Postfix) with ESMTP id B2F566B002E for ; Thu, 23 Jul 2020 23:32:44 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 326C518041E61 for ; Fri, 24 Jul 2020 03:32:44 +0000 (UTC) X-FDA: 77071547448.11.fold88_150f87c26f44 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin11.hostedemail.com (Postfix) with ESMTP id 046021803D0F6 for ; Fri, 24 Jul 2020 03:32:43 +0000 (UTC) X-HE-Tag: fold88_150f87c26f44 X-Filterd-Recvd-Size: 5996 Received: from mail-qt1-f194.google.com (mail-qt1-f194.google.com [209.85.160.194]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Fri, 24 Jul 2020 03:32:43 +0000 (UTC) Received: by mail-qt1-f194.google.com with SMTP id d27so6024253qtg.4 for ; Thu, 23 Jul 2020 20:32:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=DtcH1eTSgDszis0K7FXJ1OIRE9d5R8EpJXxCpjozCEs=; b=UA/Edbu+dhtvk4WBnl7FYJzN1RWqJ9JCjXCSLIW8hVtUQusFBc56abTMTaTCJuBR4b FVuxxneBZrZ8w+IxP8SomsV6jFyeEQxnlEG9Mo1RuD0NNeGJMRRs+AuWbd0Z2bUNrdx9 PN/B17zT6quEeH7LB8I8Ja2IJ3hwuXI1hJ9kU5mkPgQG6uAxEOfvEFdnYfpXUbJepnnQ UyphCL9W88aQRNCKJh2KTochD6+S26lPE6BREfP+abUnOMJzb1bOKuRC6aj+rg7ciPIK yfJOKQcmngIelhtdTab84BM3YC7KmmiUTUamk+AvOwMKe1mEW7EWAB/IjsCTXUOmWqr6 0t5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=DtcH1eTSgDszis0K7FXJ1OIRE9d5R8EpJXxCpjozCEs=; b=JyYM+son17I/YbpcZ+O7wjwiIGjepaJUBry2AMKoQqozltgNjq+Exc5KuYAYqsKhuJ 4JaDOV7Qf2yk8BfrHOMK7FboxFSGdDjdtzFqud69vJU5pcvMiSu3pL9ZhBcX6fhcg1xe GE3z0P0RBHmNWfzbN0qbrfMA4zMaUMz3kA67oOj9PhjhtmJsxooD7TvUDmi2Hd2XR40/ I2wHsltjTmAbnJnhusvuk7za8q2iItTAPk4r7zddqTjzdCw+/CyIpSvOjUvJnlkByGB/ HTnQNl4PKDtgQygDG4jBmqTMqu3mwhKbOEryPD4wszvLOSajtNNJXOTRdJ8ua2SViK6b xfJw== X-Gm-Message-State: AOAM530IolXc2uzQ4BsOBWQPzqX1XSx/wT1jTHkW2qkhgUGmC4VRZK06 j7uv8FIekE4kt178dwGYtRSmIhmnKFsVAZC/V9Y= X-Google-Smtp-Source: ABdhPJwEn6kqyyLS60CluVwRJCMjkbqAvw20TguZLXgpyUxcMz4OI16TOCT7v39gd4+3OKfY2jKnWs9Xqi14PLWLfYQ= X-Received: by 2002:ac8:4d0c:: with SMTP id w12mr6645053qtv.194.1595561562872; Thu, 23 Jul 2020 20:32:42 -0700 (PDT) MIME-Version: 1.0 References: <1595468942-29687-1-git-send-email-iamjoonsoo.kim@lge.com> <20200723180814.acde28b92ce6adc785a79120@linux-foundation.org> <20200723193600.28e3eedd00925b22f7ca9780@linux-foundation.org> <20200723201404.f76ccd792c9e74f3ae8ec9f5@linux-foundation.org> In-Reply-To: <20200723201404.f76ccd792c9e74f3ae8ec9f5@linux-foundation.org> From: Joonsoo Kim Date: Fri, 24 Jul 2020 12:32:31 +0900 Message-ID: Subject: Re: [PATCH v2] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs To: Andrew Morton 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 046021803D0F6 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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: 2020=EB=85=84 7=EC=9B=94 24=EC=9D=BC (=EA=B8=88) =EC=98=A4=ED=9B=84 12:14, = Andrew Morton =EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84= =B1: > > 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) > > > > Thanks for the pointer! > > > > 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. > > > > 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. Okay. It's appreciated if you remove the stable tag. Or, I will send it aga= in without the stable tag. Thanks.