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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DBFFDC32772 for ; Tue, 16 Aug 2022 06:58:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231299AbiHPG6p (ORCPT ); Tue, 16 Aug 2022 02:58:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229999AbiHPG55 (ORCPT ); Tue, 16 Aug 2022 02:57:57 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75C01E992F for ; Mon, 15 Aug 2022 19:20:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660616450; x=1692152450; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=OvL9/IKf/g+zRmxGRGIODU/Jn6YGizzjnlk8aW6h8us=; b=fKVzXYEkQUf7FpAeprSFq/o7lL+9br0kaum4XEKS+qf6J26kcN+VawIv y+woMpE059uLkr/5G/xFqjSTQmTS/g+zoZH460DK6bKFOfie/BYbjjtYk mXjemEKMnrwP7IG34dhPXteNVWAlvn4NmvGaO2YtqQnmYk8JTCiK7OCiY 5ViG5gFz7kKof9kDSYBJtA7VraK5/Qou0/AfU6g3O2s6uSY6IoOaCoGCk sIu3t8vsjwt9MfeU/oGTJD0bh8EBllCSZy2I2q+Gxil4Y7dVPOXpAGOCk /VyQFX3hIbxwAtSj3WLsXPFiCmbFtXBbpfYyMekeAAdT8KS3sIhdLbkkx Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10440"; a="378396212" X-IronPort-AV: E=Sophos;i="5.93,240,1654585200"; d="scan'208";a="378396212" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Aug 2022 19:20:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,240,1654585200"; d="scan'208";a="934706650" Received: from sse-cse-haiyue-nuc.sh.intel.com ([10.239.241.114]) by fmsmga005.fm.intel.com with ESMTP; 15 Aug 2022 19:20:47 -0700 From: Haiyue Wang To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, david@redhat.com, apopple@nvidia.com, linmiaohe@huawei.com, ying.huang@intel.com, songmuchun@bytedance.com, naoya.horiguchi@linux.dev, alex.sierra@amd.com, Haiyue Wang Subject: [PATCH v6 1/2] mm: migration: fix the FOLL_GET failure on following huge page Date: Tue, 16 Aug 2022 10:21:00 +0800 Message-Id: <20220816022102.582865-2-haiyue.wang@intel.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220816022102.582865-1-haiyue.wang@intel.com> References: <20220812084921.409142-1-haiyue.wang@intel.com> <20220816022102.582865-1-haiyue.wang@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Not all huge page APIs support FOLL_GET option, so move_pages() syscall will fail to get the page node information for some huge pages. Like x86 on linux 5.19 with 1GB huge page API follow_huge_pud(), it will return NULL page for FOLL_GET when calling move_pages() syscall with the NULL 'nodes' parameter, the 'status' parameter has '-2' error in array. Note: follow_huge_pud() now supports FOLL_GET in linux 6.0. Link: https://lore.kernel.org/all/20220714042420.1847125-3-naoya.horiguchi@linux.dev But these huge page APIs don't support FOLL_GET: 1. follow_huge_pud() in arch/s390/mm/hugetlbpage.c 2. follow_huge_addr() in arch/ia64/mm/hugetlbpage.c It will cause WARN_ON_ONCE for FOLL_GET. 3. follow_huge_pgd() in mm/hugetlb.c This is an temporary solution to mitigate the side effect of the race condition fix by calling follow_page() with FOLL_GET set for huge pages. After supporting follow huge page by FOLL_GET is done, this fix can be reverted safely. Fixes: 4cd614841c06 ("mm: migration: fix possible do_pages_stat_array racing with memory offline") Signed-off-by: Haiyue Wang Reviewed-by: "Huang, Ying" --- mm/migrate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 6a1597c92261..581dfaad9257 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1848,6 +1848,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, for (i = 0; i < nr_pages; i++) { unsigned long addr = (unsigned long)(*pages); + unsigned int foll_flags = FOLL_DUMP; struct vm_area_struct *vma; struct page *page; int err = -EFAULT; @@ -1856,8 +1857,12 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, if (!vma) goto set_status; + /* Not all huge page follow APIs support 'FOLL_GET' */ + if (!is_vm_hugetlb_page(vma)) + foll_flags |= FOLL_GET; + /* FOLL_DUMP to ignore special (like zero) pages */ - page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); + page = follow_page(vma, addr, foll_flags); err = PTR_ERR(page); if (IS_ERR(page)) @@ -1865,7 +1870,8 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, if (page && !is_zone_device_page(page)) { err = page_to_nid(page); - put_page(page); + if (foll_flags & FOLL_GET) + put_page(page); } else { err = -ENOENT; } -- 2.37.2