From patchwork Thu Aug 20 09:19:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 265348 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=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,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 4863BC433DF for ; Thu, 20 Aug 2020 13:09:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09122207DA for ; Thu, 20 Aug 2020 13:09:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597928941; bh=RIldGl/NiVmZD2dD0ICB8X/+h9ZTyBmOkIhIjpCU9cg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=a0IqQQPVhbHqPYat3EXPxUmBEOEKQ/M+NheBm3mH+UroaUjOj08BqqVUomhhVfyvc mKWTM501VWwXeegQQZPaS2fRPDKluMz5ySS00c/unBVfd5aqaPuXAePQspNfQ6DMxq ytlpjo3FbE3Gz/2pGnS0dM22aHD92pgW7aoWv68A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728781AbgHTNI5 (ORCPT ); Thu, 20 Aug 2020 09:08:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:54384 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728780AbgHTJho (ORCPT ); Thu, 20 Aug 2020 05:37:44 -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 42E40207DE; Thu, 20 Aug 2020 09:37:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597916263; bh=RIldGl/NiVmZD2dD0ICB8X/+h9ZTyBmOkIhIjpCU9cg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j6DVriTw/vQvf4NWZp6cB19KHJBCH0BapCqD373A1pZCnMFcayh7Zu5ki046NbV9X 5xWp69PiRJT+yeaxwwwEGIXevEldErLqzz3jz/v9YX9rkH3ZDfgsU6Fy5bQFpVnaHZ 3WLtESQg/G45xtZisdC02xdw3kOOWO10ts93LzAM= 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 5.7 068/204] mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible Date: Thu, 20 Aug 2020 11:19:25 +0200 Message-Id: <20200820091609.654487420@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091606.194320503@linuxfoundation.org> References: <20200820091606.194320503@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: Greg Kroah-Hartman --- mm/hugetlb.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5201,25 +5201,21 @@ 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); } /*