From nobody Tue Jun 30 01:42:48 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70FF7C433F5 for ; Fri, 28 Jan 2022 05:59:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346266AbiA1F7w (ORCPT ); Fri, 28 Jan 2022 00:59:52 -0500 Received: from mga04.intel.com ([192.55.52.120]:17301 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235697AbiA1F7v (ORCPT ); Fri, 28 Jan 2022 00:59:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1643349591; x=1674885591; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=Y9j8XokzjsNGd2nOqWcvF1wdvX3sTQQLglF93VDFjPA=; b=V2qh4zX9+zbaDP8od/+S1uq0X1ZdKwo42IlbkJVs2v2B92YUlw57ZP3I tNKRw3sfYbOeQ15XbhLOjMdiToE2Xvw+H0VCMH6QOk4FWXgu+I3MHvJBG 6xbhO3PuiqkPdE8xTi5SwQoHlJ1VPYjP8GuOPg62eLDgw/ioJ6bom0AtF F4/GEEdWW/c0dN1G1KZqlAQ7gPNtXZl+mAKvqwnpbfy07riX/R+Ajtkhm jIaawgHz82UaVaf3AgMcJ573c9KjXQ9SiP3EsOHpoSnFbX2bo5loT4gZc I1qQDtSrIDGMqiKELvzQadScxG68drQwiKwE1VOHnDJp3Ca3zpGv83Aic A==; X-IronPort-AV: E=McAfee;i="6200,9189,10240"; a="245894986" X-IronPort-AV: E=Sophos;i="5.88,322,1635231600"; d="scan'208";a="245894986" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2022 21:59:51 -0800 X-IronPort-AV: E=Sophos;i="5.88,322,1635231600"; d="scan'208";a="536004956" Received: from yhuang6-desk2.sh.intel.com ([10.239.13.11]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2022 21:59:48 -0800 From: Huang Ying To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Baolin Wang , Dave Hansen , Zi Yan , Oscar Salvador , Yang Shi , zhongjiang-ali , Xunlei Pang Subject: [PATCH] mm,migrate: fix establishing demotion target Date: Fri, 28 Jan 2022 13:59:40 +0800 Message-Id: <20220128055940.1792614-1-ying.huang@intel.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In commit ac16ec835314 ("mm: migrate: support multiple target nodes demotion"), after the first demotion target node is found, we will continue to check the next candidate obtained via find_next_best_node(). This is to find all demotion target nodes with same NUMA distance. But one side effect of find_next_best_node() is that the candidate node returned will be set in "used" parameter, even if the candidate node isn't passed in the following NUMA distance checking, the candidate node will not be used as demotion target node for the following nodes. For example, for system as follows, node distances: node 0 1 2 3 0: 10 21 17 28 1: 21 10 28 17 2: 17 28 10 28 3: 28 17 28 10 when we establish demotion target node for node 0, in the first round node 2 is added to the demotion target node set. Then in the second round, node 3 is checked and failed because distance(0, 3) > distance(0, 2). But node 3 is set in "used" nodemask too. When we establish demotion target node for node 1, there is no available node. This is wrong, node 3 should be set as the demotion target of node 1. To fix this, if the candidate node is failed to pass the distance checking, it will be cleared in "used" nodemask. So that it can be used for the following node. The bug can be reproduced and fixed with this patch on a 2 socket server machine with DRAM and PMEM. Fixes: ac16ec835314 ("mm: migrate: support multiple target nodes demotion") Signed-off-by: "Huang, Ying" Cc: Baolin Wang Cc: Dave Hansen Cc: Zi Yan Cc: Oscar Salvador Cc: Yang Shi Cc: Baolin Wang Cc: zhongjiang-ali Cc: Xunlei Pang Reviewed-by: Baolin Wang --- mm/migrate.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index c7da064b4781..e8a6933af68d 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -3082,18 +3082,21 @@ static int establish_migrate_target(int node, nodem= ask_t *used, if (best_distance !=3D -1) { val =3D node_distance(node, migration_target); if (val > best_distance) - return NUMA_NO_NODE; + goto out_clear; } =20 index =3D nd->nr; if (WARN_ONCE(index >=3D DEMOTION_TARGET_NODES, "Exceeds maximum demotion target nodes\n")) - return NUMA_NO_NODE; + goto out_clear; =20 nd->nodes[index] =3D migration_target; nd->nr++; =20 return migration_target; +out_clear: + node_clear(migration_target, *used); + return NUMA_NO_NODE; } =20 /* --=20 2.30.2