From patchwork Wed Apr 6 22:51:00 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Kirill A. Shutemov" X-Patchwork-Id: 8766941 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 19429C0554 for ; Wed, 6 Apr 2016 22:59:16 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 43241200E6 for ; Wed, 6 Apr 2016 22:59:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 620C120172 for ; Wed, 6 Apr 2016 22:59:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754973AbcDFW6L (ORCPT ); Wed, 6 Apr 2016 18:58:11 -0400 Received: from mga04.intel.com ([192.55.52.120]:19302 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754467AbcDFWvd (ORCPT ); Wed, 6 Apr 2016 18:51:33 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga104.fm.intel.com with ESMTP; 06 Apr 2016 15:51:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,448,1455004800"; d="scan'208";a="80454656" Received: from black.fi.intel.com ([10.237.72.93]) by fmsmga004.fm.intel.com with ESMTP; 06 Apr 2016 15:51:28 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id 2798D505; Thu, 7 Apr 2016 01:51:22 +0300 (EEST) From: "Kirill A. Shutemov" To: Hugh Dickins , Andrea Arcangeli , Andrew Morton Cc: Dave Hansen , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Jerome Marchand , Yang Shi , Sasha Levin , Andres Lagar-Cavilla , Ning Qu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv6 10/30] thp: handle file COW faults Date: Thu, 7 Apr 2016 01:51:00 +0300 Message-Id: <1459983080-106718-11-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: <1459983080-106718-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1459983080-106718-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP File COW for THP is handled on pte level: just split the pmd. It's not clear how benefitial would be allocation of huge pages on COW faults. And it would require some code to make them work. I think at some point we can consider teaching khugepaged to collapse pages in COW mappings, but allocating huge on fault is probably overkill. Signed-off-by: Kirill A. Shutemov --- mm/memory.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index c41804c0d524..e5c6b4387da3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3395,6 +3395,11 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) if (fe->vma->vm_ops->pmd_fault) return fe->vma->vm_ops->pmd_fault(fe->vma, fe->address, fe->pmd, fe->flags); + + /* 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; }