From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755987Ab1JQOmf (ORCPT ); Mon, 17 Oct 2011 10:42:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1321 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751076Ab1JQOme (ORCPT ); Mon, 17 Oct 2011 10:42:34 -0400 From: Andrea Arcangeli To: Peter Zijlstra Cc: Andrew Morton , Minchan Kim , Michel Lespinasse , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , KOSAKI Motohiro , Shaohua Li , "Paul E. McKenney" , Benjamin Herrenschmidt Subject: [PATCH 1/3] s390: gup_huge_pmd() support THP tail recounting Date: Mon, 17 Oct 2011 16:41:55 +0200 Message-Id: <1318862517-7042-2-git-send-email-aarcange@redhat.com> In-Reply-To: <1318862517-7042-1-git-send-email-aarcange@redhat.com> References: <1316793432.9084.47.camel@twins> <1318862517-7042-1-git-send-email-aarcange@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Up to this point the code assumed old refcounting for hugepages (pre-thp). This updates the code directly to the thp mapcount tail page refcounting. Signed-off-by: Andrea Arcangeli --- arch/s390/mm/gup.c | 24 +++++++++++++++++++++++- 1 files changed, 23 insertions(+), 1 deletions(-) diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c index 45b405c..668dda9 100644 --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -48,11 +48,22 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, return 1; } +static inline void get_huge_page_tail(struct page *page) +{ + /* + * __split_huge_page_refcount() cannot run + * from under us. + */ + VM_BUG_ON(page_mapcount(page) < 0); + VM_BUG_ON(atomic_read(&page->_count) != 0); + atomic_inc(&page->_mapcount); +} + static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { unsigned long mask, result; - struct page *head, *page; + struct page *head, *page, *tail; int refs; result = write ? 0 : _SEGMENT_ENTRY_RO; @@ -64,6 +75,7 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, refs = 0; head = pmd_page(pmd); page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + tail = page; do { VM_BUG_ON(compound_head(page) != head); pages[*nr] = page; @@ -81,6 +93,16 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, *nr -= refs; while (refs--) put_page(head); + } else { + /* + * Any tail page need their mapcount reference taken + * before we return. + */ + while (refs--) { + if (PageTail(tail)) + get_huge_page_tail(tail); + tail++; + } } return 1;