From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f70.google.com (mail-it0-f70.google.com [209.85.214.70]) by kanga.kvack.org (Postfix) with ESMTP id AA74C6B0033 for ; Sat, 4 Nov 2017 12:31:54 -0400 (EDT) Received: by mail-it0-f70.google.com with SMTP id 72so1180245itl.1 for ; Sat, 04 Nov 2017 09:31:54 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id f78sor2685259ita.133.2017.11.04.09.31.53 for (Google Transport Security); Sat, 04 Nov 2017 09:31:53 -0700 (PDT) Subject: Re: [PATCH 04/15] brd: remove dax support 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 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: owner-linux-mm@kvack.org List-ID: 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 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 -- 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