From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=DATE_IN_FUTURE_06_12, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3CEFC76190 for ; Tue, 23 Jul 2019 03:08:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B80892238E for ; Tue, 23 Jul 2019 03:08:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387901AbfGWDIo (ORCPT ); Mon, 22 Jul 2019 23:08:44 -0400 Received: from ex13-edg-ou-001.vmware.com ([208.91.0.189]:12328 "EHLO EX13-EDG-OU-001.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387875AbfGWDIl (ORCPT ); Mon, 22 Jul 2019 23:08:41 -0400 Received: from sc9-mailhost2.vmware.com (10.113.161.72) by EX13-EDG-OU-001.vmware.com (10.113.208.155) with Microsoft SMTP Server id 15.0.1156.6; Mon, 22 Jul 2019 20:08:22 -0700 Received: from akaher-lnx-dev.eng.vmware.com (unknown [10.110.19.203]) by sc9-mailhost2.vmware.com (Postfix) with ESMTP id 10E83B24DB; Mon, 22 Jul 2019 23:08:34 -0400 (EDT) From: Ajay Kaher To: CC: , , , , , , , , , , , , , , , , , , "Kirill A. Shutemov" , Naoya Horiguchi , Steve Capper , Johannes Weiner , Christoph Lameter , David Rientjes , Andrew Morton Subject: [PATCH 3/8] mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton Date: Tue, 23 Jul 2019 16:38:26 +0530 Message-ID: <1563880111-19058-4-git-send-email-akaher@vmware.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1563880111-19058-1-git-send-email-akaher@vmware.com> References: <1563880111-19058-1-git-send-email-akaher@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-001.vmware.com: akaher@vmware.com does not designate permitted sender hosts) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" commit 7aef4172c7957d7e65fc172be4c99becaef855d4 upstream. With new refcounting we are going to see THP tail pages mapped with PTE. Generic fast GUP rely on page_cache_get_speculative() to obtain reference on page. page_cache_get_speculative() always fails on tail pages, because ->_count on tail pages is always zero. Let's handle tail pages in gup_pte_range(). New split_huge_page() will rely on migration entries to freeze page's counts. Recheck PTE value after page_cache_get_speculative() on head page should be enough to serialize against split. Signed-off-by: Kirill A. Shutemov Tested-by: Sasha Levin Tested-by: Aneesh Kumar K.V Acked-by: Jerome Marchand Acked-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Dave Hansen Cc: Mel Gorman Cc: Rik van Riel Cc: Naoya Horiguchi Cc: Steve Capper Cc: Johannes Weiner Cc: Michal Hocko Cc: Christoph Lameter Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ajay Kaher --- mm/gup.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 2cd3b31..45c544b 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1070,7 +1070,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, * for an example see gup_get_pte in arch/x86/mm/gup.c */ pte_t pte = READ_ONCE(*ptep); - struct page *page; + struct page *head, *page; /* * Similar to the PMD case below, NUMA hinting must take slow @@ -1082,15 +1082,17 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); + head = compound_head(page); - if (!page_cache_get_speculative(page)) + if (!page_cache_get_speculative(head)) goto pte_unmap; if (unlikely(pte_val(pte) != pte_val(*ptep))) { - put_page(page); + put_page(head); goto pte_unmap; } + VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++; -- 2.7.4