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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 8A946C433E1 for ; Wed, 15 Jul 2020 12:35:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7179320658 for ; Wed, 15 Jul 2020 12:35:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729808AbgGOMfb (ORCPT ); Wed, 15 Jul 2020 08:35:31 -0400 Received: from mga03.intel.com ([134.134.136.65]:62591 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726396AbgGOMfb (ORCPT ); Wed, 15 Jul 2020 08:35:31 -0400 IronPort-SDR: +SEn2+9Cb6d3w4Vj9YylY/R2YfUJgU2u+idsTD2WOyrubosPlSWBXqigVnIoi+KkvpmgVBLmns 91ln9iiYL9yg== X-IronPort-AV: E=McAfee;i="6000,8403,9682"; a="149130062" X-IronPort-AV: E=Sophos;i="5.75,355,1589266800"; d="scan'208";a="149130062" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jul 2020 05:35:17 -0700 IronPort-SDR: GFVku8FxPuBhbJwckGG+97wqo1oklR5rxjArhU0zj/kScG7/CZXpWNSSdIK5U+PaP39ZUjSj5Y qUMlHCtEVM+w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,355,1589266800"; d="scan'208";a="268943784" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga007.fm.intel.com with ESMTP; 15 Jul 2020 05:35:15 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id D95A2190; Wed, 15 Jul 2020 15:35:14 +0300 (EEST) From: "Kirill A. Shutemov" To: Andrew Morton Cc: Linus Torvalds , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Naresh Kamboju , Joel Fernandes , William Kucharski Subject: [PATCH] mm: Fix warning in move_normal_pmd() Date: Wed, 15 Jul 2020 15:35:13 +0300 Message-Id: <20200715123513.42240-1-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org mremap(2) does not allow source and destination regions to overlap, but shift_arg_pages() calls move_page_tables() directly and in this case the source and destination overlap often. It confuses move_normal_pmd(): WARNING: CPU: 3 PID: 27091 at mm/mremap.c:211 move_page_tables+0x6ef/0x720 move_normal_pmd() expects the destination PMD to be empty, but when ranges overlap nobody removes PTE page tables on source side. move_ptes() only removes PTE entries, leaving tables behind. When the source PMD becomes destination and alignment/size is right we step onto the warning. The warning is harmless: kernel correctly fallbacks to handle entries on per-entry basis. The fix is to avoid move_normal_pmd() if we see that source and destination ranges overlap. Signed-off-by: Kirill A. Shutemov Reported-and-tested-by: Naresh Kamboju Fixes: 2c91bd4a4e2e ("mm: speed up mremap by 20x on large regions") Cc: Joel Fernandes Cc: William Kucharski --- mm/mremap.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index 5dd572d57ca9..e33fcee541fe 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -245,6 +245,18 @@ unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long extent, next, old_end; struct mmu_notifier_range range; pmd_t *old_pmd, *new_pmd; + bool overlaps; + + /* + * shift_arg_pages() can call move_page_tables() on overlapping ranges. + * In this case we cannot use move_normal_pmd() because destination pmd + * might be established page table: move_ptes() doesn't free page + * table. + */ + if (old_addr > new_addr) + overlaps = old_addr - new_addr < len; + else + overlaps = new_addr - old_addr < len; old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end); @@ -282,7 +294,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma, split_huge_pmd(vma, old_pmd, old_addr); if (pmd_trans_unstable(old_pmd)) continue; - } else if (extent == PMD_SIZE) { + } else if (!overlaps && extent == PMD_SIZE) { #ifdef CONFIG_HAVE_MOVE_PMD /* * If the extent is PMD-sized, try to speed the move by -- 2.26.2