From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752308AbeEOHwY (ORCPT ); Tue, 15 May 2018 03:52:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:43995 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752155AbeEOHwX (ORCPT ); Tue, 15 May 2018 03:52:23 -0400 Date: Tue, 15 May 2018 09:52:21 +0200 From: Johannes Thumshirn To: Christoph Hellwig Cc: Keith Busch , Sagi Grimberg , Linux NVMe Mailinglist , Linux Kernel Mailinglist , Hannes Reinecke Subject: Re: [PATCH 3/5] nvme: call nvmf_create_ctrl before checking for duplicate assignment Message-ID: <20180515075221.4ppaxdvbosy36ltk@linux-x5ow.site> References: <20180515074043.22843-1-jthumshirn@suse.de> <20180515074043.22843-4-jthumshirn@suse.de> <20180515075055.GB23659@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180515075055.GB23659@lst.de> User-Agent: NeoMutt/20170912 (1.9.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 15, 2018 at 09:50:55AM +0200, Christoph Hellwig wrote: > On Tue, May 15, 2018 at 09:40:41AM +0200, Johannes Thumshirn wrote: > > In nvmf_dev_write we did check if the /dev/nvme-fabrics device node's > > private data is already set and then create a controller data > > structure afterwards. The private data is protected by the > > nvmf_dev_mutex, but there is no need to hold it while calling > > nvmf_create_ctrl(). > > > > This also reduces the number of lockdep complaints in the 'nvme > > connect' with fcloop scenario. > > Something looks seriously fishy in fcloop. How do we and up in > a RCU critical section here? __blk_mq_run_hw_queue() calls blk_mq_sched_dispatch_requests() with the hctx_lock() a.k.a rcu_read_lock() held. nvmf_connect_admin_queue() does I/O which causes the above to be called. > In general it seems like fc loop needs to offload any I/O to a workqueue > just like nvme-loop does, but even then I can't see how that is going to > cause an issue in this area. Hmm I'll be looking into it. -- Johannes Thumshirn Storage jthumshirn@suse.de +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850