From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id B3E6F6B025E for ; Tue, 21 Nov 2017 18:05:06 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id v186so1880392wma.9 for ; Tue, 21 Nov 2017 15:05:06 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id z1si11483899wre.339.2017.11.21.15.05.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Nov 2017 15:05:05 -0800 (PST) Date: Tue, 21 Nov 2017 15:05:01 -0800 From: Andrew Morton Subject: Re: [PATCH v2 1/4] mm: introduce get_user_pages_longterm Message-Id: <20171121150501.d4d811a66444cb5c9cb85bf2@linux-foundation.org> In-Reply-To: <151068939435.7446.13560129395419350737.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151068938905.7446.12333914805308312313.stgit@dwillia2-desk3.amr.corp.intel.com> <151068939435.7446.13560129395419350737.stgit@dwillia2-desk3.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Hellwig , stable@vger.kernel.org, linux-nvdimm@lists.01.org On Tue, 14 Nov 2017 11:56:34 -0800 Dan Williams wrote: > Until there is a solution to the dma-to-dax vs truncate problem it is > not safe to allow long standing memory registrations against > filesytem-dax vmas. Device-dax vmas do not have this problem and are > explicitly allowed. > > This is temporary until a "memory registration with layout-lease" > mechanism can be implemented for the affected sub-systems (RDMA and > V4L2). Sounds like that will be unpleasant. Do we really need it to be that complex? Can we get away with simply failing the get_user_pages() request? Or are there significant usecases for RDMA and V4L to play with DAX memory? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org