From patchwork Wed May 17 17:16:38 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ross Zwisler X-Patchwork-Id: 9731731 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8FB616022E for ; Wed, 17 May 2017 17:21:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 94A0528689 for ; Wed, 17 May 2017 17:21:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8864F287D3; Wed, 17 May 2017 17:21:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1ABD928689 for ; Wed, 17 May 2017 17:21:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753034AbdEQRSK (ORCPT ); Wed, 17 May 2017 13:18:10 -0400 Received: from mga11.intel.com ([192.55.52.93]:26481 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751716AbdEQRQ4 (ORCPT ); Wed, 17 May 2017 13:16:56 -0400 Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 May 2017 10:16:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.38,355,1491289200"; d="scan'208";a="102912393" Received: from theros.lm.intel.com ([10.232.112.77]) by fmsmga005.fm.intel.com with ESMTP; 17 May 2017 10:16:54 -0700 From: Ross Zwisler To: Andrew Morton , linux-kernel@vger.kernel.org Cc: Ross Zwisler , "Darrick J. Wong" , Alexander Viro , Christoph Hellwig , Dan Williams , Dave Hansen , Jan Kara , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, "Kirill A . Shutemov" , Pawel Lebioda , Dave Jiang , Xiong Zhou , Eryu Guan , stable@vger.kernel.org Subject: [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages Date: Wed, 17 May 2017 11:16:38 -0600 Message-Id: <20170517171639.14501-1-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.9.4 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When the pmd_devmap() checks were added by: commit 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd") to add better support for DAX huge pages, they were all added to the end of if() statements after existing pmd_trans_huge() checks. So, things like: - if (pmd_trans_huge(*pmd)) + if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) When further checks were added after pmd_trans_unstable() checks by: commit 7267ec008b5c ("mm: postpone page table allocation until we have page to map") they were also added at the end of the conditional: + if (pmd_trans_unstable(fe->pmd) || pmd_devmap(*fe->pmd)) This ordering is fine for pmd_trans_huge(), but doesn't work for pmd_trans_unstable(). This is because DAX huge pages trip the bad_pmd() check inside of pmd_none_or_trans_huge_or_clear_bad() (called by pmd_trans_unstable()), which prints out a warning and returns 1. So, we do end up doing the right thing, but only after spamming dmesg with suspicious looking messages: mm/pgtable-generic.c:39: bad pmd ffff8808daa49b88(84000001006000a5) Reorder these checks so that pmd_devmap() is checked first, avoiding the error messages. Signed-off-by: Ross Zwisler Fixes: commit 7267ec008b5c ("mm: postpone page table allocation until we have page to map") Cc: stable@vger.kernel.org Reviewed-by: Jan Kara --- mm/memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 6ff5d72..1ee269d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3061,7 +3061,7 @@ static int pte_alloc_one_map(struct vm_fault *vmf) * through an atomic read in C, which is what pmd_trans_unstable() * provides. */ - if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd)) + if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd)) return VM_FAULT_NOPAGE; vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, @@ -3690,7 +3690,7 @@ static int handle_pte_fault(struct vm_fault *vmf) vmf->pte = NULL; } else { /* See comment in pte_alloc_one_map() */ - if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd)) + if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd)) return 0; /* * A regular pmd is established and it can't morph into a huge