From patchwork Fri Aug 7 06:26:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 266731 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 3AD69C433E1 for ; Fri, 7 Aug 2020 06:26:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07B5622D08 for ; Fri, 7 Aug 2020 06:26:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781575; bh=9vvKDgJBhmzpnVGlr68RQj6uv0/viRH/J2s/tIT/nEI=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=OkMOwAWs3ka8XkpwJSPr/nQJpKO8l0e+3uCKOuP88wK0Ym49qEGDv4sUA4qDnpl4x ujTp06aUn6YmXbRADB5PsL8ouBpq+pHBMF5A7Apn4rOvYas80Sa0CKivEKolwI17xM sbo/zPdlZwTjGT671ShGG2H7Q2f+YZHovk4/DJhU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726256AbgHGG0O (ORCPT ); Fri, 7 Aug 2020 02:26:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:34738 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbgHGG0N (ORCPT ); Fri, 7 Aug 2020 02:26:13 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 7140222D07; Fri, 7 Aug 2020 06:26:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781572; bh=9vvKDgJBhmzpnVGlr68RQj6uv0/viRH/J2s/tIT/nEI=; h=Date:From:To:Subject:In-Reply-To:From; b=a4g+Y6A011ftX0aX5yfLd9TjTdvHz+k/6/3a6E9wVVQetmWPC0EPetpepwDCy5teH Qdxj1pN60obk5rDaWXKGd+XrtH1PKVNXdjkXcS2WCuGorPzG3ZaINPzSyjGO8ZW84j QAIlx5noJnrZTuBsd5qLw+GWRW/eCyMOl/may8IY= Date: Thu, 06 Aug 2020 23:26:11 -0700 From: Andrew Morton To: aarcange@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, peterx@redhat.com, stable@vger.kernel.org, torvalds@linux-foundation.org, willy@infradead.org Subject: [patch 157/163] mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible Message-ID: <20200807062611.RGbHdqUiZ%akpm@linux-foundation.org> In-Reply-To: <20200806231643.a2711a608dd0f18bff2caf2b@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 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); } /*