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=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,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 60866C33CB1 for ; Sat, 18 Jan 2020 05:32:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 14CD824673 for ; Sat, 18 Jan 2020 05:32:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DgH3J6aq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14CD824673 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 AA5746B0520; Sat, 18 Jan 2020 00:32:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A2EBB6B0521; Sat, 18 Jan 2020 00:32:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F6C06B0522; Sat, 18 Jan 2020 00:32:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0175.hostedemail.com [216.40.44.175]) by kanga.kvack.org (Postfix) with ESMTP id 7692A6B0520 for ; Sat, 18 Jan 2020 00:32:48 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 0EFB845A3 for ; Sat, 18 Jan 2020 05:32:48 +0000 (UTC) X-FDA: 76389635616.14.jar13_529f0f733b703 X-HE-Tag: jar13_529f0f733b703 X-Filterd-Recvd-Size: 5189 Received: from mail-ed1-f65.google.com (mail-ed1-f65.google.com [209.85.208.65]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Sat, 18 Jan 2020 05:32:47 +0000 (UTC) Received: by mail-ed1-f65.google.com with SMTP id l8so24326602edw.1 for ; Fri, 17 Jan 2020 21:32:47 -0800 (PST) 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; bh=iGO7As1ACatxG0Km9ZDObq/5CWcC4DDbVgvTHZSZ69o=; b=DgH3J6aqNr0SkIyXXTWbwvdqt0OSx9ziGjcKa8VB0bSCWxoOhFl1CG5Bu2Mrxa/OMZ Qphe7I5cjOrzlZHUChYTKg+aExR0QSq6bRJgALzZomhzCXGQzbaIMECerEYW+UL/zLha 79nEXY0MWSUF09nC7pAXctcZW4MqcsaUqdPOYJ/BkcF1G1OElMNWOPy9FmkUJMdvkETe GmNnPw7OpbLd+wS93b5Qrw7m2e38Gu6kRnu8nFb436xSs3PVm0CLd8tncBLhRR6Nczcz ePiyC7PeYJan7JagiXZB7fR8qoe0orag9C2iaxrS/NQamL8vWtBOWRBXQ1X0Ui29BDEa wMYg== 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; bh=iGO7As1ACatxG0Km9ZDObq/5CWcC4DDbVgvTHZSZ69o=; b=qQn6+YLSOxMRYdUS0ymt4NbdS4ilGNJPFJJUEROJaLUW5fvM2BvJmSF7tTE4qm1HcP qT4QLtzW4RAREBYA5NHp3tgcEONbYHw2FkkG4nmsRFtv5Kd+z/FNkWvW0vzzt/F3tB7C 2wSn9jeFXN0nyJovl9boyYGYEwivVTweNkuctPIy9DFXrEZfhC+v7dHPM7EAMxerGLmX q4Go8mL74GdgttELeNfjZp+UyOZrfFs9QukGX7HdIf0CPlvMCB/Y+jdMXRD+wiPSfCkV hURUQ74ONBahJGDUy6xWG7xVTWdVuqfn5lgD2R4RQXzQoAzFpZWwdg3FkoYmQCeKSkQW PSWQ== X-Gm-Message-State: APjAAAU1kLGPRrheGVk4j+/KbsBllU2mSC7Led6+EW7ozmcpTQVTyf99 qPOyFyE+ZB7cnKDT3nB9L5s6T67qUoxxUEhhXL0= X-Google-Smtp-Source: APXvYqzjMlhU6tPuIqThx7vP/9qBNYifikvYJ+ycVTF4/jxz3XJWZSdykWesD0CMM/78tWPC5NflAQSvZDBTwcstrVI= X-Received: by 2002:a50:ba83:: with SMTP id x3mr7442375ede.206.1579325566598; Fri, 17 Jan 2020 21:32:46 -0800 (PST) MIME-Version: 1.0 References: <20200117074534.25324-1-richardw.yang@linux.intel.com> <20200117222740.GB29229@richard> In-Reply-To: From: Yang Shi Date: Fri, 17 Jan 2020 21:32:32 -0800 Message-ID: Subject: Re: [PATCH] mm/migrate.c: also overwrite error when it is bigger than zero To: Wei Yang Cc: Andrew Morton , Linux MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" 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, Jan 17, 2020 at 3:30 PM Yang Shi wrote: > > On Fri, Jan 17, 2020 at 2:27 PM Wei Yang wrote: > > > > On Fri, Jan 17, 2020 at 03:45:34PM +0800, Wei Yang wrote: > > >If we get here after successfully adding page to list, err would be > > >the number of pages in the list. > > > > > >Current code has two problems: > > > > > > * on success, 0 is not returned > > > * on error, the real error code is not returned > > > > > > > Well, this breaks the user interface. User would receive 1 even the migration > > succeed. > > > > The change is introduced by e0153fc2c760 ("mm: move_pages: return valid node > > id in status if the page is already on the target node"). > > Yes, it may return a value which is > 0. But, it seems do_pages_move() > could return > 0 value even before this commit. > > For example, if I read the code correctly, it would do: > > If we already have some pages on the queue then > add_page_for_migration() return error, then do_move_pages_to_node() is > called, but it may return > 0 value (the number of pages that were > *not* migrated by migrate_pages()), then the code flow would just jump > to "out" and return the value. And, it may happen to be 1. Just figured out this is another regression introduced by a49bd4d71637 ("mm, numa: rework do_pages_move"). Already posted a patch to fix it. > > I'm not sure if it breaks the user interface since the behavior has > been existed for years, and it looks nobody complains about it. Maybe > glibc helps hide it or people just care if it is 0 and the status. > > > > > >Signed-off-by: Wei Yang > > >--- > > > mm/migrate.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > >diff --git a/mm/migrate.c b/mm/migrate.c > > >index 557da996b936..c3ef70de5876 100644 > > >--- a/mm/migrate.c > > >+++ b/mm/migrate.c > > >@@ -1677,7 +1677,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, > > > err1 = do_move_pages_to_node(mm, &pagelist, current_node); > > > if (!err1) > > > err1 = store_status(status, start, current_node, i - start); > > >- if (!err) > > >+ if (err >= 0) > > > err = err1; > > > out: > > > return err; > > >-- > > >2.17.1 > > > > -- > > Wei Yang > > Help you, Help me > >