From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F807C63777 for ; Mon, 30 Nov 2020 07:37:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B4D920709 for ; Mon, 30 Nov 2020 07:37:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725902AbgK3HhD (ORCPT ); Mon, 30 Nov 2020 02:37:03 -0500 Received: from mx2.suse.de ([195.135.220.15]:50970 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725860AbgK3HhD (ORCPT ); Mon, 30 Nov 2020 02:37:03 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 09E40AC6A; Mon, 30 Nov 2020 07:36:21 +0000 (UTC) Subject: Re: [PATCH 25/45] block: simplify bdev/disk lookup in blkdev_get To: Christoph Hellwig , Jens Axboe Cc: Tejun Heo , Josef Bacik , Coly Li , Mike Snitzer , Greg Kroah-Hartman , Jan Kara , Johannes Thumshirn , dm-devel@redhat.com, Jan Kara , linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20201128161510.347752-1-hch@lst.de> <20201128161510.347752-26-hch@lst.de> From: Hannes Reinecke Message-ID: Date: Mon, 30 Nov 2020 08:36:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201128161510.347752-26-hch@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 11/28/20 5:14 PM, Christoph Hellwig wrote: > To simplify block device lookup and a few other upcoming areas, make sure > that we always have a struct block_device available for each disk and > each partition, and only find existing block devices in bdget. The only > downside of this is that each device and partition uses a little more > memory. The upside will be that a lot of code can be simplified. > > With that all we need to look up the block device is to lookup the inode > and do a few sanity checks on the gendisk, instead of the separate lookup > for the gendisk. For blk-cgroup which wants to access a gendisk without > opening it, a new blkdev_{get,put}_no_open low-level interface is added > to replace the previous get_gendisk use. > > Note that the change to look up block device directly instead of the two > step lookup using struct gendisk causes a subtile change in behavior: > accessing a non-existing partition on an existing block device can now > cause a call to request_module. That call is harmless, and in practice > no recent system will access these nodes as they aren't created by udev > and static /dev/ setups are unusual. > > Signed-off-by: Christoph Hellwig > --- > block/blk-cgroup.c | 42 ++++---- > block/blk-iocost.c | 36 +++---- > block/blk.h | 2 +- > block/genhd.c | 210 +++++-------------------------------- > block/partitions/core.c | 29 ++--- > fs/block_dev.c | 177 +++++++++++++++++-------------- > include/linux/blk-cgroup.h | 4 +- > include/linux/blkdev.h | 6 ++ > include/linux/genhd.h | 7 +- > 9 files changed, 194 insertions(+), 319 deletions(-) > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer