From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753372AbdK0QPQ (ORCPT ); Mon, 27 Nov 2017 11:15:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:37930 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752895AbdK0QPO (ORCPT ); Mon, 27 Nov 2017 11:15:14 -0500 Date: Mon, 27 Nov 2017 17:15:11 +0100 From: Jan Kara To: Dan Williams Cc: akpm@linux-foundation.org, Jan Kara , Joonyoung Shim , linux-nvdimm@lists.01.org, Seung-Woo Kim , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Inki Dae , linux-mm@kvack.org, Kyungmin Park , Mel Gorman , Mauro Carvalho Chehab , Vlastimil Babka , linux-media@vger.kernel.org Subject: Re: [PATCH v2 2/4] mm: fail get_vaddr_frames() for filesystem-dax mappings Message-ID: <20171127161511.GE5977@quack2.suse.cz> References: <151068938905.7446.12333914805308312313.stgit@dwillia2-desk3.amr.corp.intel.com> <151068939985.7446.15684639617389154187.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151068939985.7446.15684639617389154187.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 14-11-17 11:56:39, Dan Williams wrote: > Until there is a solution to the dma-to-dax vs truncate problem it is > not safe to allow V4L2, Exynos, and other frame vector users to create > long standing / irrevocable memory registrations against filesytem-dax > vmas. > > Cc: Inki Dae > Cc: Seung-Woo Kim > Cc: Joonyoung Shim > Cc: Kyungmin Park > Cc: Mauro Carvalho Chehab > Cc: linux-media@vger.kernel.org > Cc: Jan Kara > Cc: Mel Gorman > Cc: Vlastimil Babka > Cc: Andrew Morton > Cc: > Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") > Signed-off-by: Dan Williams Makes sense. I'd just note that in principle get_vaddr_frames() is no more long-term than get_user_pages(). It is just so that all the users of get_vaddr_frames() currently want a long-term reference. Maybe could you add here also a comment that the vma_is_fsdax() check is there because all users of this function want a long term page reference? With that you can add: Reviewed-by: Jan Kara Honza > --- > mm/frame_vector.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/frame_vector.c b/mm/frame_vector.c > index 72ebec18629c..d2fdbeaadc8b 100644 > --- a/mm/frame_vector.c > +++ b/mm/frame_vector.c > @@ -52,6 +52,10 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > ret = -EFAULT; > goto out; > } > + > + if (vma_is_fsdax(vma)) > + return -EOPNOTSUPP; > + > if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { > vec->got_ref = true; > vec->is_pfns = false; > -- Jan Kara SUSE Labs, CR