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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham 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 50C5AC2D0C0 for ; Mon, 23 Dec 2019 22:31:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2ABD5206CB for ; Mon, 23 Dec 2019 22:31:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726903AbfLWWbH (ORCPT ); Mon, 23 Dec 2019 17:31:07 -0500 Received: from mga14.intel.com ([192.55.52.115]:52759 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726817AbfLWWbG (ORCPT ); Mon, 23 Dec 2019 17:31:06 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Dec 2019 14:30:52 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,349,1571727600"; d="scan'208";a="207404142" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga007.jf.intel.com with ESMTP; 23 Dec 2019 14:30:51 -0800 From: Wei Yang To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com, Wei Yang Subject: [Patch v2] mm/rmap.c: split huge pmd when it really is Date: Tue, 24 Dec 2019 06:28:56 +0800 Message-Id: <20191223222856.7189-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When page is not NULL, function is called by try_to_unmap_one() with TTU_SPLIT_HUGE_PMD set. There are two cases to call try_to_unmap_one() with TTU_SPLIT_HUGE_PMD set: * unmap_page() * shrink_page_list() In both case, the page passed to try_to_unmap_one() is PageHead() of the THP. If this page's mapping address in process is not HPAGE_PMD_SIZE aligned, this means the THP is not mapped as PMD THP in this process. This could happen when we do mremap() a PMD size range to an un-aligned address. Currently, this case is handled by following check in __split_huge_pmd() luckily. page != pmd_page(*pmd) This patch checks the address to skip some work. Signed-off-by: Wei Yang --- v2: move the check into split_huge_pmd_address(). --- mm/huge_memory.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 893fecd5daa4..2b9c2f412b32 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2342,6 +2342,22 @@ void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, pud_t *pud; pmd_t *pmd; + /* + * When page is not NULL, function is called by try_to_unmap_one() + * with TTU_SPLIT_HUGE_PMD set. There are two places set + * TTU_SPLIT_HUGE_PMD + * + * unmap_page() + * shrink_page_list() + * + * In both cases, the "page" here is the PageHead() of a THP. + * + * If the page is not a PMD mapped huge page, e.g. after mremap(), it + * is not necessary to split it. + */ + if (page && !IS_ALIGNED(address, HPAGE_PMD_SIZE)) + return; + pgd = pgd_offset(vma->vm_mm, address); if (!pgd_present(*pgd)) return; -- 2.17.1