From patchwork Mon Aug 24 08:32:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 265121 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=-10.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, 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 2ADE9C433DF for ; Mon, 24 Aug 2020 08:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 02A5E2072D for ; Mon, 24 Aug 2020 08:57:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259471; bh=0vyft/VSgrnMagMT2usHlPRU18zZUjsnEaD7djZEAtk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=biuH97Um1ZTPsxcHlYIHTWdAK9B1Yo81eK1ocJUPwShI8c4vKMJTNfIEjc3mPnq/j kE6mmLHW3qSvuJc3A1WrKdTewpNwHTG/l7QMn6S8iiwC7yF3u5WkYFcK1ZMCYBKfnP vPPBWrZf9Ht6B6279IUfbFMrur00P/Bq20KwPG3g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730712AbgHXI5q (ORCPT ); Mon, 24 Aug 2020 04:57:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:45210 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729951AbgHXI5q (ORCPT ); Mon, 24 Aug 2020 04:57:46 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A38872074D; Mon, 24 Aug 2020 08:57:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259465; bh=0vyft/VSgrnMagMT2usHlPRU18zZUjsnEaD7djZEAtk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cMCamHSJweqJpUNPgq7ouceWPE/udYgYCPk2uN+1LMKSpLpFKW4AcTc3wzjQsGRtx OLNUkFT5Qlz2Tat/5Adv7AdwW2V70ZLGyGVg16VCyWHhRXGqWpwcefdcwHwGrPuhau bHrBprB3cZnF5jx9pyOWYyzeurgwHTpukFvrZHmw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Xu , Andrew Morton , Mike Kravetz , Andrea Arcangeli , Matthew Wilcox , Linus Torvalds Subject: [PATCH 4.19 69/71] mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible Date: Mon, 24 Aug 2020 10:32:00 +0200 Message-Id: <20200824082359.416421024@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082355.848475917@linuxfoundation.org> References: <20200824082355.848475917@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Xu commit 75802ca66354a39ab8e35822747cd08b3384a99a upstream. This is found by code observation only. Firstly, the worst case scenario should assume the whole range was covered by pmd sharing. The old algorithm might not work as expected for ranges like (1g-2m, 1g+2m), where the adjusted range should be (0, 1g+2m) but the expected range should be (0, 2g). Since at it, remove the loop since it should not be required. With that, the new code should be faster too when the invalidating range is huge. Mike said: : With range (1g-2m, 1g+2m) within a vma (0, 2g) the existing code will only : adjust to (0, 1g+2m) which is incorrect. : : We should cc stable. The original reason for adjusting the range was to : prevent data corruption (getting wrong page). Since the range is not : always adjusted correctly, the potential for corruption still exists. : : However, I am fairly confident that adjust_range_if_pmd_sharing_possible : is only gong to be called in two cases: : : 1) for a single page : 2) for range == entire vma : : In those cases, the current code should produce the correct results. : : To be safe, let's just cc stable. Fixes: 017b1660df89 ("mm: migration: fix migration of huge PMD shared pages") Signed-off-by: Peter Xu Signed-off-by: Andrew Morton Reviewed-by: Mike Kravetz Cc: Andrea Arcangeli Cc: Matthew Wilcox Cc: Link: http://lkml.kernel.org/r/20200730201636.74778-1-peterx@redhat.com Signed-off-by: Linus Torvalds Signed-off-by: Mike Kravetz Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4650,25 +4650,21 @@ static bool vma_shareable(struct vm_area void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, unsigned long *start, unsigned long *end) { - unsigned long check_addr = *start; + unsigned long a_start, a_end; if (!(vma->vm_flags & VM_MAYSHARE)) return; - for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { - unsigned long a_start = check_addr & PUD_MASK; - unsigned long a_end = a_start + PUD_SIZE; + /* Extend the range to be PUD aligned for a worst case scenario */ + a_start = ALIGN_DOWN(*start, PUD_SIZE); + a_end = ALIGN(*end, PUD_SIZE); - /* - * If sharing is possible, adjust start/end if necessary. - */ - if (range_in_vma(vma, a_start, a_end)) { - if (a_start < *start) - *start = a_start; - if (a_end > *end) - *end = a_end; - } - } + /* + * Intersect the range with the vma range, since pmd sharing won't be + * across vma after all + */ + *start = max(vma->vm_start, a_start); + *end = min(vma->vm_end, a_end); } /*