From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by kanga.kvack.org (Postfix) with ESMTP id 4FA1C6B026C for ; Wed, 6 Apr 2016 18:51:43 -0400 (EDT) Received: by mail-pa0-f48.google.com with SMTP id zm5so41724876pac.0 for ; Wed, 06 Apr 2016 15:51:43 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id x80si7272057pfi.97.2016.04.06.15.51.31 for ; Wed, 06 Apr 2016 15:51:31 -0700 (PDT) From: "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> 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: 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 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; } -- 2.8.0.rc3 -- 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