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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 8D6E7C2D0A3 for ; Thu, 29 Oct 2020 10:02:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1923A2076E for ; Thu, 29 Oct 2020 10:02:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="UIAwvXhE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725788AbgJ2KCC (ORCPT ); Thu, 29 Oct 2020 06:02:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725554AbgJ2KCC (ORCPT ); Thu, 29 Oct 2020 06:02:02 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB4CCC0613CF; Thu, 29 Oct 2020 03:02:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=bJJQrkz2DmvsLC/KQQtP+/G8oJcKg1SqkvfvGBG1Kis=; b=UIAwvXhE7HjAKmjqXHhRLl9xIu KdZK7e/fqvMm7rw2C3LqAZWCEoNoruvvPKUgUOyoKN58s/OwdGeINy+HwrgeVqArnWnrWryUY+jb2 royGa8LcqCMYxcXyw6E3NTJ5qcor1MUKOfrLFe6lmKdBULXWQ/gsxFST+ILBM5vpMTfivLaMPZ0n+ lwNr6d0yKwrW/JY6j7owx/oU7GPyKNkMlHL34diDPWpyASCTiVyUcN8P0tll8Al92jhTzzyoPZ7TQ SPduM45A4CaJpZqoSz2G8kug/654kfdn1ADp01H/bNB0YIohiOR0lAbAAi2em9I40rFtMfTVnxd9Z XBUKi7SQ==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kY4kn-0002hM-SZ; Thu, 29 Oct 2020 10:01:57 +0000 Date: Thu, 29 Oct 2020 10:01:57 +0000 From: Christoph Hellwig To: Daniel Vetter Cc: Christoph Hellwig , DRI Development , LKML , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , linux-s390 Subject: Re: [PATCH v4 00/15] follow_pfn and other iomap races Message-ID: <20201029100157.GA10041@infradead.org> References: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> <20201029085749.GB25658@infradead.org> <20201029092800.GA494@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Thu, Oct 29, 2020 at 10:38:16AM +0100, Daniel Vetter wrote: > Hm so Jason and me discussed this, but e.g. the s390 is safe with with > just the pagetable locks. So we'd need two versions. > > The more practical problem is that I haven't found a reasonable way to > check that a passed in mmu_notifier is registered against the mm we're > working on, and without that check it feels a bit silly. But if you > see how to do that I think we can do an EXPORT_SYMBOL_GPL follow_pfn > which takes the notifier, and an __follow_pfn for s390 and similar > internal code which isn't exported. True, this is a bit of a mess. So maybe just rename it to __follow_pfn, proper documentation of the requirements and a switch to EXPORT_SYMBOL_GPL.