From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932728AbcCNWun (ORCPT ); Mon, 14 Mar 2016 18:50:43 -0400 Received: from mga02.intel.com ([134.134.136.20]:20116 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932361AbcCNWum (ORCPT ); Mon, 14 Mar 2016 18:50:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,337,1455004800"; d="scan'208";a="933768535" Date: Mon, 14 Mar 2016 16:50:17 -0600 From: Ross Zwisler To: NeilBrown Cc: Keith Busch , Maxim Levitsky , Vishal Verma , Jens Axboe , Dan Williams , Ross Zwisler , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-nvdimm@ml01.01.org Subject: Re: [PATCH 0/4] Remove un-needed 'major' registration when alloc_disk(0) is used. Message-ID: <20160314225017.GC19926@linux.intel.com> References: <20160309215702.20904.61407.stgit@noble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160309215702.20904.61407.stgit@noble> 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 Thu, Mar 10, 2016 at 08:59:28AM +1100, NeilBrown wrote: > When alloc_disk(0) is used, the ->major number is ignored and > irrelevant. Yet several drivers register a major number anyway. > > This series of patches removes the pointless registrations. The pmem > driver also does this, but a patch has already been sent for that > driver. > > Note that I am not in a position to test these beyond simple compile > testing. > > Thanks, > NeilBrown > > > --- > > NeilBrown (4): > nvdimm/blk: don't allocate unused major device number > nvdimm/btt: don't allocate unused major device number > memstick: don't allocate unused major for ms_block > NVMe: don't allocate unused nvme_major > > > drivers/memstick/core/ms_block.c | 17 ++--------------- > drivers/nvdimm/blk.c | 18 +----------------- > drivers/nvdimm/btt.c | 19 ++----------------- > drivers/nvme/host/core.c | 16 +--------------- > 4 files changed, 6 insertions(+), 64 deletions(-) There are several other drivers that allocate a major, but then use it for some small number of minors (1 for null_blk.c and 16 for virtio_blk.c). They both have GENHD_FL_EXT_DEVT set, so I think what happens is that after we exhaust the allocated minors they hop over to having BLOCK_EXT_MAJOR as a major and a dynamically assigned minor. It seems like these could easily be converted in the same way so they'd use BLOCK_EXT_MAJOR for their major and have a bunch of dynamically assigned minors. Does this break something I'm not seeing? Yay for this series, by the way. :)