From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 Date: Thu, 29 Oct 2020 10:01:57 +0000 From: Christoph Hellwig 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: List-ID: 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 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.