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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50C5CCCA483 for ; Mon, 13 Jun 2022 11:05:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351394AbiFMLED (ORCPT ); Mon, 13 Jun 2022 07:04:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350043AbiFMKyj (ORCPT ); Mon, 13 Jun 2022 06:54:39 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3880DFB8; Mon, 13 Jun 2022 03:28:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 65D87B80E90; Mon, 13 Jun 2022 10:28:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B52B9C34114; Mon, 13 Jun 2022 10:28:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655116121; bh=HBg/U462XO0GEQkKUAxLoJKOElZL0qi7ivJM+jX5lzE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UQ9brzMsOnaqRmAJz+Ill5tIMjVm43MVawQzF6chBt7w6u+ESezzHFtFF+U0TgJBF bVI8C9O/cydGUA1lvKEjLsFtzWx/+Fi0PyqB2RKNyOQtaCwxv5DLafCLe3QhNYkc7d Evi1R2xd1eytvU4sXI501C3COAvvf6q/oYsovSfw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mike Kravetz , Muchun Song , Andrew Morton Subject: [PATCH 4.14 127/218] hugetlb: fix huge_pmd_unshare address update Date: Mon, 13 Jun 2022 12:09:45 +0200 Message-Id: <20220613094924.427329322@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094908.257446132@linuxfoundation.org> References: <20220613094908.257446132@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Kravetz commit 48381273f8734d28ef56a5bdf1966dd8530111bc upstream. The routine huge_pmd_unshare() is passed a pointer to an address associated with an area which may be unshared. If unshare is successful this address is updated to 'optimize' callers iterating over huge page addresses. For the optimization to work correctly, address should be updated to the last huge page in the unmapped/unshared area. However, in the common case where the passed address is PUD_SIZE aligned, the address is incorrectly updated to the address of the preceding huge page. That wastes CPU cycles as the unmapped/unshared range is scanned twice. Link: https://lkml.kernel.org/r/20220524205003.126184-1-mike.kravetz@oracle.com Fixes: 39dde65c9940 ("shared page table for hugetlb page") Signed-off-by: Mike Kravetz Acked-by: Muchun Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4798,7 +4798,14 @@ int huge_pmd_unshare(struct mm_struct *m pud_clear(pud); put_page(virt_to_page(ptep)); mm_dec_nr_pmds(mm); - *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE; + /* + * This update of passed address optimizes loops sequentially + * processing addresses in increments of huge page size (PMD_SIZE + * in this case). By clearing the pud, a PUD_SIZE area is unmapped. + * Update address to the 'last page' in the cleared area so that + * calling loop can move to first page past this area. + */ + *addr |= PUD_SIZE - PMD_SIZE; return 1; } #define want_pmd_share() (1)