From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S976681AbdDXSNO (ORCPT ); Mon, 24 Apr 2017 14:13:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54922 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S976627AbdDXSMy (ORCPT ); Mon, 24 Apr 2017 14:12:54 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com BD914C059752 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jglisse@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com BD914C059752 From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: John Hubbard , Naoya Horiguchi , David Nellans , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Ross Zwisler Subject: [HMM 02/15] mm/put_page: move ZONE_DEVICE page reference decrement v2 Date: Mon, 24 Apr 2017 14:12:30 -0400 Message-Id: <20170424181243.20320-3-jglisse@redhat.com> In-Reply-To: <20170424181243.20320-1-jglisse@redhat.com> References: <20170424181243.20320-1-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 24 Apr 2017 18:12:54 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Move page reference decrement of ZONE_DEVICE from put_page() to put_zone_device_page() this does not affect non ZONE_DEVICE page. Doing this allow to catch when a ZONE_DEVICE page refcount reach 1 which means the device is no longer reference by any one (unlike page from other zone, ZONE_DEVICE page refcount never reach 0). This patch is just a preparatory patch for HMM. Changes since v1: - commit message Signed-off-by: Jérôme Glisse Reviewed-by: Dan Williams Cc: Ross Zwisler --- include/linux/mm.h | 14 +++++++++++--- kernel/memremap.c | 6 ++++++ 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index c82e8db..022423c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -821,11 +821,19 @@ static inline void put_page(struct page *page) { page = compound_head(page); + /* + * ZONE_DEVICE pages should never have their refcount reach 0 (this + * would be a bug), so call page_ref_dec() in put_zone_device_page() + * to decrement page refcount and skip __put_page() here, as this + * would worsen things if a ZONE_DEVICE had a refcount bug. + */ + if (unlikely(is_zone_device_page(page))) { + put_zone_device_page(page); + return; + } + if (put_page_testzero(page)) __put_page(page); - - if (unlikely(is_zone_device_page(page))) - put_zone_device_page(page); } #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) diff --git a/kernel/memremap.c b/kernel/memremap.c index ea714ee..97ef676 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -190,6 +190,12 @@ EXPORT_SYMBOL(get_zone_device_page); void put_zone_device_page(struct page *page) { + /* + * ZONE_DEVICE page refcount should never reach 0 and never be freed + * to kernel memory allocator. + */ + page_ref_dec(page); + put_dev_pagemap(page->pgmap); } EXPORT_SYMBOL(put_zone_device_page); -- 2.9.3