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 02515C33C9E for ; Fri, 17 Jan 2020 23:30:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B00912073A for ; Fri, 17 Jan 2020 23:30:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JmbDAwbX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B00912073A 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 2B6206B050E; Fri, 17 Jan 2020 18:30:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 265896B050F; Fri, 17 Jan 2020 18:30:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 17CD76B0510; Fri, 17 Jan 2020 18:30:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id 016E16B050E for ; Fri, 17 Jan 2020 18:30:33 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id CD1E9181AEF07 for ; Fri, 17 Jan 2020 23:30:33 +0000 (UTC) X-FDA: 76388722746.07.run77_7948dbe683048 X-HE-Tag: run77_7948dbe683048 X-Filterd-Recvd-Size: 4749 Received: from mail-ed1-f65.google.com (mail-ed1-f65.google.com [209.85.208.65]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Fri, 17 Jan 2020 23:30:33 +0000 (UTC) Received: by mail-ed1-f65.google.com with SMTP id t17so23851453eds.6 for ; Fri, 17 Jan 2020 15:30:33 -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=nCCYlDZcNgoml+0c24ZO2L5zKWUXiA9cZ58LrpH144k=; b=JmbDAwbXXB5RGvmeRg1WWAAKeyjsZZBtJ08W4tZoEk/CSrnPguZJgGe2lioXMXhfBL DCgGnk7oH10mqvkcDu5pSs5RGo0HXJ41X+4w2Zyw2HzVoy28e9v2ArnZUYbZa1qfh0n2 X+b79T707SNPzogQ9MC8LHjmEuIZAvSTjKpKFd4UFOJG/m0fiw8W707oUNKKqGHzMNzB 8Dt/aZeQ8u+LZ1zaemJmg4kn5PYxYeJ88m7bq6i+dg5TNdaoYaLY8jV1ZCutWGZ4r9+f v3iTWfxX/ovKWcAgvz669ECNXk90D2lMcAj7Md8GQWG8kdfVvjkvmCvMp04vho3Hii4g jeVw== 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=nCCYlDZcNgoml+0c24ZO2L5zKWUXiA9cZ58LrpH144k=; b=XgKInDYtVqe4YuJemHWIXFIGvipD4SsmDeiKU6jFoAGQ5rqhfez5iO2+sRjW0AncDF tTjGeyZEoL2G6WnP4PcM99R+jgYlNa30CnhXEBGa8qsIfOHODl0+Kceus0bLJyos4JZi SzE0FB+t1rW8YUdVLbEC/asmTN8Hf/HnRtt2IY+uijPA+MvNKMOvwBmCfp5cjyN6VlHb ptFnqTqSOLudNLrdcxMg/DS0bJ9OnmnvXa2JONbgVbaTH9+gVz3U8AsbiBvK6FZL6UH4 r/L/lHQkJcSAkV560HKL8qN4Y5m2P1MttGwvRBg+hyQ+wD2+EhEEcZNudWV5Fc37Fvd4 J0UA== X-Gm-Message-State: APjAAAVEqOAdxO/2lBNtUSFgD7nF6iD6xbn059ILh8Yyf3VSo9xNlWzk cwFlNrjJOXAkAHreEXLwxm0PJutuKC5wvWDwA38= X-Google-Smtp-Source: APXvYqzhO1sFOcgNuTNHMKBeKa5gMZ8L8WbFoYEU0kh57iLsbmtrLICnJDVQuCNyUQt/E8nUqaOLJxDGpcdDzZ5prVI= X-Received: by 2002:aa7:de05:: with SMTP id h5mr6553530edv.343.1579303832030; Fri, 17 Jan 2020 15:30:32 -0800 (PST) MIME-Version: 1.0 References: <20200117074534.25324-1-richardw.yang@linux.intel.com> <20200117222740.GB29229@richard> In-Reply-To: <20200117222740.GB29229@richard> From: Yang Shi Date: Fri, 17 Jan 2020 15:30:18 -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 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. 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 >