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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 60E53C43444 for ; Thu, 3 Jan 2019 14:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DBDB208E3 for ; Thu, 3 Jan 2019 14:39:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QeyuFHan" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732007AbfACOjL (ORCPT ); Thu, 3 Jan 2019 09:39:11 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:53852 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729142AbfACOjK (ORCPT ); Thu, 3 Jan 2019 09:39:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=cpyYqlHvB58KkTNoC4Cjl0Icxb9x69XoxiEczy+KqYM=; b=QeyuFHanBW2Kzy081ggKqX4ggH /m7IpUxJmN7r/ckut+rupPEL+CmUISmVKcKsPzF3rdjPXdAlhLPhaDIHkPTfy3K+I0xG7M2fZoNzQ nKbMiMdqRF7I1Bc2ixOTX49RjW5PBwWON5MRRPTgSsY9rxCvV7jjBIEgZY41tsSPCrcX4TU6j5aVy vjzj3wd0oac0bB/muKz4HmcuzXGqMtsOh/z/uctUETDNmJ/y7kDoCVbYs+Rr6R+WPfHRNi7H9Fwuy i13FAUsfiP6y8irSP5MruWSXGbn1nRz29KptoYAHfJhcMd9UnSldtYSQiBBlU+7tkSQnCZxSYfeCr ytgjmakA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gf49N-0001F0-0s; Thu, 03 Jan 2019 14:39:09 +0000 Date: Thu, 3 Jan 2019 06:39:08 -0800 From: Matthew Wilcox To: Jerome Glisse Cc: John Hubbard , Andrew Morton , linux-mm@kvack.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, Christian =?iso-8859-1?Q?K=F6nig?= , Jan Kara Subject: Re: [PATCH] Initialise mmu_notifier_range correctly Message-ID: <20190103143908.GQ6310@bombadil.infradead.org> References: <20190103002126.GM6310@bombadil.infradead.org> <20190103015654.GB15619@redhat.com> <785af237-eb67-c304-595d-9080a2f48102@nvidia.com> <20190103041833.GN6310@bombadil.infradead.org> <20190103142959.GA3395@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190103142959.GA3395@redhat.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 03, 2019 at 09:29:59AM -0500, Jerome Glisse wrote: > On Wed, Jan 02, 2019 at 08:18:33PM -0800, Matthew Wilcox wrote: > > On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote: > > > Having the range struct declared in separate places from the mmu_notifier_range_init() > > > calls is not great. But I'm not sure I see a way to make it significantly cleaner, given > > > that __follow_pte_pmd uses the range pointer as a way to decide to issue the mmn calls. > > > > Yeah, I don't think there's anything we can do. But I started reviewing > > the comments, and they don't make sense together: > > > > /* > > * Note because we provide range to follow_pte_pmd it will > > * call mmu_notifier_invalidate_range_start() on our behalf > > * before taking any lock. > > */ > > if (follow_pte_pmd(vma->vm_mm, address, &range, > > &ptep, &pmdp, &ptl)) > > continue; > > > > /* > > * No need to call mmu_notifier_invalidate_range() as we are > > * downgrading page table protection not changing it to point > > * to a new page. > > * > > * See Documentation/vm/mmu_notifier.rst > > */ > > > > So if we don't call mmu_notifier_invalidate_range, why are we calling > > mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end? > > ie, why not this ... > > Thus comments looks wrong to me ... we need to call > mmu_notifier_invalidate_range() those are use by > IOMMU. I might be to blame for those comments thought. Yes, you're to blame for both of them. a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 791) * Note because we provide start/end to follow_pte_pmd it will a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 792) * call mmu_notifier_invalidate_range_start() on our behalf a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 793) * before taking any lock. 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 794) * No need to call mmu_notifier_invalidate_range() as we are 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 795) * downgrading page table protection not changing it to point 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 796) * to a new page.