From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id AC4506B0038 for ; Wed, 17 May 2017 13:16:57 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id c6so13599498pfj.5 for ; Wed, 17 May 2017 10:16:57 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTPS id d9si2621669pgn.218.2017.05.17.10.16.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 May 2017 10:16:56 -0700 (PDT) From: Ross Zwisler 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 --- 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 -- 2.9.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org