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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 F02D8C33CB1 for ; Tue, 28 Jan 2020 00:34:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C029F22527 for ; Tue, 28 Jan 2020 00:34:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C029F22527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5A6786B0007; Mon, 27 Jan 2020 19:34:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 52F6A6B0008; Mon, 27 Jan 2020 19:34:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3D08F6B000A; Mon, 27 Jan 2020 19:34:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0101.hostedemail.com [216.40.44.101]) by kanga.kvack.org (Postfix) with ESMTP id 241276B0007 for ; Mon, 27 Jan 2020 19:34:32 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id BFD8F1F1F for ; Tue, 28 Jan 2020 00:34:31 +0000 (UTC) X-FDA: 76425171942.23.group72_61abc5c46541f X-HE-Tag: group72_61abc5c46541f X-Filterd-Recvd-Size: 5363 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Tue, 28 Jan 2020 00:34:30 +0000 (UTC) X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Jan 2020 16:34:29 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,371,1574150400"; d="scan'208";a="261263777" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 27 Jan 2020 16:34:27 -0800 Date: Tue, 28 Jan 2020 08:34:40 +0800 From: Wei Yang To: Yang Shi Cc: mhocko@suse.com, richardw.yang@linux.intel.com, willy@infradead.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [v4 PATCH] mm: move_pages: report the number of non-attempted pages Message-ID: <20200128003440.GB20624@richard> Reply-To: Wei Yang References: <1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.9.4 (2018-02-28) 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 Tue, Jan 28, 2020 at 05:28:47AM +0800, Yang Shi wrote: >Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"), >the semantic of move_pages() has changed to return the number of >non-migrated pages if they were result of a non-fatal reasons (usually a >busy page). This was an unintentional change that hasn't been noticed >except for LTP tests which checked for the documented behavior. > >There are two ways to go around this change. We can even get back to the >original behavior and return -EAGAIN whenever migrate_pages is not able >to migrate pages due to non-fatal reasons. Another option would be to >simply continue with the changed semantic and extend move_pages >documentation to clarify that -errno is returned on an invalid input or >when migration simply cannot succeed (e.g. -ENOMEM, -EBUSY) or the >number of pages that couldn't have been migrated due to ephemeral >reasons (e.g. page is pinned or locked for other reasons). > >This patch implements the second option because this behavior is in >place for some time without anybody complaining and possibly new users >depending on it. Also it allows to have a slightly easier error handling >as the caller knows that it is worth to retry when err > 0. > >But since the new semantic would be aborted immediately if migration is >failed due to ephemeral reasons, need include the number of non-attempted >pages in the return value too. > >Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") >Suggested-by: Michal Hocko >Acked-by: Michal Hocko >Cc: Wei Yang >Cc: [4.17+] >Signed-off-by: Yang Shi Reviewed-by: Wei Yang >--- >v4: Fixed some typo and grammar errors caught by Willy >v3: Rephrased the commit log per Michal and added Michal's Acked-by >v2: Rebased on top of the latest mainline kernel per Andrew > > mm/migrate.c | 25 +++++++++++++++++++++++-- > 1 file changed, 23 insertions(+), 2 deletions(-) > >diff --git a/mm/migrate.c b/mm/migrate.c >index 86873b6..2530860 100644 >--- a/mm/migrate.c >+++ b/mm/migrate.c >@@ -1627,8 +1627,19 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, > start = i; > } else if (node != current_node) { > err = do_move_pages_to_node(mm, &pagelist, current_node); >- if (err) >+ if (err) { >+ /* >+ * Positive err means the number of failed >+ * pages to migrate. Since we are going to >+ * abort and return the number of non-migrated >+ * pages, so need to incude the rest of the >+ * nr_pages that have not been attempted as >+ * well. >+ */ >+ if (err > 0) >+ err += nr_pages - i - 1; > goto out; >+ } > err = store_status(status, start, current_node, i - start); > if (err) > goto out; >@@ -1659,8 +1670,11 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, > goto out_flush; > > err = do_move_pages_to_node(mm, &pagelist, current_node); >- if (err) >+ if (err) { >+ if (err > 0) >+ err += nr_pages - i - 1; > goto out; >+ } > if (i > start) { > err = store_status(status, start, current_node, i - start); > if (err) >@@ -1674,6 +1688,13 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, > > /* Make sure we do not overwrite the existing error */ > err1 = do_move_pages_to_node(mm, &pagelist, current_node); >+ /* >+ * Don't have to report non-attempted pages here since: >+ * - If the above loop is done gracefully all pages have been >+ * attempted. >+ * - If the above loop is aborted it means a fatal error >+ * happened, should return ret. >+ */ > if (!err1) > err1 = store_status(status, start, current_node, i - start); > if (!err) >-- >1.8.3.1 -- Wei Yang Help you, Help me