From patchwork Mon Jan 27 21:28:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Shi X-Patchwork-Id: 11353275 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A2AB81580 for ; Mon, 27 Jan 2020 21:29:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6DC812467C for ; Mon, 27 Jan 2020 21:29:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6DC812467C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6CE7D6B0003; Mon, 27 Jan 2020 16:29:00 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 67F836B0006; Mon, 27 Jan 2020 16:29:00 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5BB586B0007; Mon, 27 Jan 2020 16:29:00 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id 437416B0003 for ; Mon, 27 Jan 2020 16:29:00 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id E31B6180AD804 for ; Mon, 27 Jan 2020 21:28:59 +0000 (UTC) X-FDA: 76424704398.07.mom48_4e72836198a0f X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,yang.shi@linux.alibaba.com,,RULES_HIT:30034:30046:30054:30070:30091,0,RBL:47.88.44.36:@linux.alibaba.com:.lbl8.mailshell.net-62.18.0.100 64.10.201.10;47.88.44.36-irl.urbl.hostedemail.com-127.0.0.150,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:none,Custom_rules:0:1:0,LFtime:25,LUA_SUMMARY:none X-HE-Tag: mom48_4e72836198a0f X-Filterd-Recvd-Size: 4802 Received: from out4436.biz.mail.alibaba.com (out4436.biz.mail.alibaba.com [47.88.44.36]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Mon, 27 Jan 2020 21:28:58 +0000 (UTC) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0TodWSHI_1580160527; Received: from localhost(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TodWSHI_1580160527) by smtp.aliyun-inc.com(127.0.0.1); Tue, 28 Jan 2020 05:28:55 +0800 From: Yang Shi To: mhocko@suse.com, richardw.yang@linux.intel.com, willy@infradead.org, akpm@linux-foundation.org Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [v4 PATCH] mm: move_pages: report the number of non-attempted pages Date: Tue, 28 Jan 2020 05:28:47 +0800 Message-Id: <1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 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: 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)