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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 9CD20C3B186 for ; Mon, 10 Feb 2020 13:07:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77FC120708 for ; Mon, 10 Feb 2020 13:07:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581340049; bh=Ew29Lcr5t4uxLKFeZ7aqjFO7NYFvymdkq1Q/5unER/A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lgJ93UEAIoLpPM6P5dzn+3FGWoAZW2defqF+7Qd2x4DmpHons9rWXkOwJS4/KXy3I W/bA6zEjR5u6wNNmLuxfOxPecW2G4jsFQ5rwHUR1IehmENz3VVJAstdHpFgeeq2Ril lOyDBkHtYj4r5yqAgoubxj7awgyxVAOAP1qX9vYo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729582AbgBJNH2 (ORCPT ); Mon, 10 Feb 2020 08:07:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:37728 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729487AbgBJMjl (ORCPT ); Mon, 10 Feb 2020 07:39:41 -0500 Received: from localhost (unknown [209.37.97.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 06FB72465D; Mon, 10 Feb 2020 12:39:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338381; bh=Ew29Lcr5t4uxLKFeZ7aqjFO7NYFvymdkq1Q/5unER/A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xbi6irP79wF58stEnn7mbGJwtn6uQXDmzB9BReqvLWXB03F1M90v5qfHXHMrZYuoZ YANkig0n5uV/XRU6u++dByCUC3g26yNeIzZ99tOf6XOfjTiD13llafQvNbVc760aB8 zVttjWWevFGyQJ09gRHYiXt/fH1t7JR0KT2pwC/Y= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yang Shi , Michal Hocko , Wei Yang , Andrew Morton , Linus Torvalds Subject: [PATCH 5.5 060/367] mm: move_pages: report the number of non-attempted pages Date: Mon, 10 Feb 2020 04:29:33 -0800 Message-Id: <20200210122429.622029875@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200210122423.695146547@linuxfoundation.org> References: <20200210122423.695146547@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Yang Shi commit 5984fabb6e82d9ab4e6305cb99694c85d46de8ae upstream. 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. Link: http://lkml.kernel.org/r/1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") Signed-off-by: Yang Shi Suggested-by: Michal Hocko Acked-by: Michal Hocko Reviewed-by: Wei Yang Cc: [4.17+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/migrate.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1627,8 +1627,19 @@ static int do_pages_move(struct mm_struc 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_struc 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 @@ out_flush: /* 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 >= 0)