From patchwork Mon Aug 10 02:40:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 266716 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=-7.0 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,URIBL_BLOCKED autolearn=no 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 63CC5C433DF for ; Mon, 10 Aug 2020 02:40:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D0462065D for ; Mon, 10 Aug 2020 02:40:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597027229; bh=CmEyyYigoOmyKgn52QYwu6+WTrl1epM9xz+kCVbY3GQ=; h=Date:From:To:Subject:List-ID:From; b=UZ4Z1CBhahKChsc3xp8WXt5MktiksjdGDB0b5zC+JT7rE7r/rUXBidBdyvgQ1jYBx OBJfEqe8YlZer6o4oE8Os64pityYxsT2crNRMsTPsbQlDYC3WuozDHF+raYYzoFlK6 EngDfmcEsxffpwEn4E3bcM9XvqWdxzWfh03GCiP0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726428AbgHJCk2 (ORCPT ); Sun, 9 Aug 2020 22:40:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:43434 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726219AbgHJCk2 (ORCPT ); Sun, 9 Aug 2020 22:40:28 -0400 Received: from localhost.localdomain (c-71-198-47-131.hsd1.ca.comcast.net [71.198.47.131]) (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 E77FF206C3; Mon, 10 Aug 2020 02:40:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597027227; bh=CmEyyYigoOmyKgn52QYwu6+WTrl1epM9xz+kCVbY3GQ=; h=Date:From:To:Subject:From; b=2JoyNZWkwTLRp7mWPAKWavtsBSkn0yLqogeEGcCA8ap10K4aewM1kK3sqF8nKlktf iRlfYAFAtC96P3T6nzkCLAlvp73wSh+1GEvt/ukuB/h+AY7SaKBbp0WsJDk8Oz2/k4 lU6hNxokKrAnuV2v+/agKaWJ8FbryNfwvwpeNTF0= Date: Sun, 09 Aug 2020 19:40:26 -0700 From: akpm@linux-foundation.org To: aarcange@redhat.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, peterx@redhat.com, stable@vger.kernel.org, willy@infradead.org Subject: [merged] mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch removed from -mm tree Message-ID: <20200810024026.NYpa6jXx0%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible has been removed from the -mm tree. Its filename was mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Peter Xu Subject: mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible 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. Link: http://lkml.kernel.org/r/20200730201636.74778-1-peterx@redhat.com Fixes: 017b1660df89 ("mm: migration: fix migration of huge PMD shared pages") Signed-off-by: Peter Xu Reviewed-by: Mike Kravetz Cc: Andrea Arcangeli Cc: Matthew Wilcox Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) --- a/mm/hugetlb.c~mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible +++ a/mm/hugetlb.c @@ -5314,25 +5314,21 @@ 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; + 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); } /*