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 1028EC2D0C0 for ; Mon, 23 Dec 2019 22:30:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C26CF206CB for ; Mon, 23 Dec 2019 22:30:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C26CF206CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6E2538E0005; Mon, 23 Dec 2019 17:30:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 66B258E0001; Mon, 23 Dec 2019 17:30:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 559348E0005; Mon, 23 Dec 2019 17:30:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0023.hostedemail.com [216.40.44.23]) by kanga.kvack.org (Postfix) with ESMTP id 3D5E18E0001 for ; Mon, 23 Dec 2019 17:30:54 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id DF0E2180AD80F for ; Mon, 23 Dec 2019 22:30:53 +0000 (UTC) X-FDA: 76297852386.08.flesh85_24de12cad155b X-HE-Tag: flesh85_24de12cad155b X-Filterd-Recvd-Size: 2801 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Mon, 23 Dec 2019 22:30:53 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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