Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941219AbcJYAOc (ORCPT ); Mon, 24 Oct 2016 20:14:32 -0400 Received: from mga01.intel.com ([192.55.52.88]:1912 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758139AbcJYAOQ (ORCPT ); Mon, 24 Oct 2016 20:14:16 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,543,1473145200"; d="scan'208";a="893532101" From: "Kirill A. Shutemov" To: "Theodore Ts'o" , Andreas Dilger , Jan Kara , Andrew Morton Cc: Alexander Viro , Hugh Dickins , Andrea Arcangeli , Dave Hansen , Vlastimil Babka , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv4 11/43] thp: handle write-protection faults for file THP Date: Tue, 25 Oct 2016 03:13:10 +0300 Message-Id: <20161025001342.76126-12-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20161025001342.76126-1-kirill.shutemov@linux.intel.com> References: <20161025001342.76126-1-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1135 Lines: 37 For filesystems that wants to be write-notified (has mkwrite), we will encount write-protection faults for huge PMDs in shared mappings. The easiest way to handle them is to clear the PMD and let it refault as wriable. Signed-off-by: Kirill A. Shutemov Reviewed-by: Jan Kara --- mm/memory.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index e18c57bdc75c..e8c04d1d87b8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3452,8 +3452,17 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) return fe->vma->vm_ops->pmd_fault(fe->vma, fe->address, fe->pmd, fe->flags); + if (fe->vma->vm_flags & VM_SHARED) { + /* Clear PMD */ + zap_page_range_single(fe->vma, fe->address & HPAGE_PMD_MASK, + HPAGE_PMD_SIZE, NULL); + VM_BUG_ON(!pmd_none(*fe->pmd)); + + /* Refault to establish writable PMD */ + return 0; + } + /* COW handled on pte level: split pmd */ - VM_BUG_ON_VMA(fe->vma->vm_flags & VM_SHARED, fe->vma); split_huge_pmd(fe->vma, fe->pmd, fe->address); return VM_FAULT_FALLBACK; -- 2.9.3