From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753804AbbKWUKJ (ORCPT ); Mon, 23 Nov 2015 15:10:09 -0500 Received: from g2t1383g.austin.hp.com ([15.217.136.92]:32650 "EHLO g2t1383g.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768AbbKWUKH (ORCPT ); Mon, 23 Nov 2015 15:10:07 -0500 From: Toshi Kani To: dan.j.williams@intel.com Cc: kirill.shutemov@linux.intel.com, willy@linux.intel.com, ross.zwisler@linux.intel.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@ml01.01.org, linux-kernel@vger.kernel.org, Toshi Kani Subject: [PATCH] dax: Split pmd map when fallback on COW Date: Mon, 23 Nov 2015 13:05:20 -0700 Message-Id: <1448309120-20911-1-git-send-email-toshi.kani@hpe.com> X-Mailer: git-send-email 2.4.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org An infinite loop of PMD faults was observed when attempted to mlock() a private read-only PMD mmap'd range of a DAX file. __dax_pmd_fault() simply returns with VM_FAULT_FALLBACK when falling back to PTE on COW. However, __handle_mm_fault() returns without falling back to handle_pte_fault() because a PMD map is present in this case. Change __dax_pmd_fault() to split the PMD map, if present, before returning with VM_FAULT_FALLBACK. Signed-off-by: Toshi Kani Cc: Dan Williams Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Ross Zwisler --- fs/dax.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index 43671b6..3405583 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -546,8 +546,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, return VM_FAULT_FALLBACK; /* Fall back to PTEs if we're going to COW */ - if (write && !(vma->vm_flags & VM_SHARED)) + if (write && !(vma->vm_flags & VM_SHARED)) { + split_huge_page_pmd(vma, address, pmd); return VM_FAULT_FALLBACK; + } /* If the PMD would extend outside the VMA */ if (pmd_addr < vma->vm_start) return VM_FAULT_FALLBACK;