From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f199.google.com (mail-ob0-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id 1D75E6B0266 for ; Tue, 7 Jun 2016 07:01:20 -0400 (EDT) Received: by mail-ob0-f199.google.com with SMTP id yu3so916658obb.3 for ; Tue, 07 Jun 2016 04:01:20 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTP id f10si34490098pfj.137.2016.06.07.04.01.01 for ; Tue, 07 Jun 2016 04:01:02 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv9-rebased 10/32] thp: handle file COW faults Date: Tue, 7 Jun 2016 14:00:24 +0300 Message-Id: <1465297246-98985-11-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1465297246-98985-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1465222029-45942-1-git-send-email-kirill.shutemov@linux.intel.com> <1465297246-98985-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: 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" 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 7f2e16e9f0cb..a9501e2851d8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3466,6 +3466,11 @@ 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; } -- 2.8.1 -- 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