From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752665AbdKDQb4 (ORCPT ); Sat, 4 Nov 2017 12:31:56 -0400 Received: from mail-it0-f43.google.com ([209.85.214.43]:47165 "EHLO mail-it0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751945AbdKDQby (ORCPT ); Sat, 4 Nov 2017 12:31:54 -0400 X-Google-Smtp-Source: ABhQp+TxYRIN6B9sF4geM1k50oujhJeZRW8ddyIUD1AcDYXDaJPHOOiJFANyOL8mH2tFKWnAf8vKZg== Subject: Re: [PATCH 04/15] brd: remove dax support To: Dan Williams , linux-nvdimm@lists.01.org Cc: akpm@linux-foundation.org, Matthew Wilcox , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Ross Zwisler , hch@lst.de References: <150949209290.24061.6283157778959640151.stgit@dwillia2-desk3.amr.corp.intel.com> <150949211688.24061.1197869674847507598.stgit@dwillia2-desk3.amr.corp.intel.com> From: Jens Axboe Message-ID: <74de4b5f-eacd-9058-45e6-d7fcfb2f0d51@kernel.dk> Date: Sat, 4 Nov 2017 10:31:51 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <150949211688.24061.1197869674847507598.stgit@dwillia2-desk3.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/31/2017 05:21 PM, Dan Williams wrote: > DAX support in brd is awkward because its backing page frames are > distinct from the ones provided by pmem, dcssblk, or axonram. We need > pfn_t_devmap() entries to fully support DAX, and the limited DAX support > for pfn_t_special() page frames is not interesting for brd when pmem is > already a superset of brd. Lastly, brd is the only dax capable driver > that may sleep in its ->direct_access() implementation. So it causes a > global burden with no net gain of kernel functionality. > > For all these reasons, remove DAX support. Reviewed-by: Jens Axboe -- Jens Axboe