Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756081AbdC2K6Y (ORCPT ); Wed, 29 Mar 2017 06:58:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:33717 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756078AbdC2Kzx (ORCPT ); Wed, 29 Mar 2017 06:55:53 -0400 Date: Wed, 29 Mar 2017 12:55:36 +0200 From: Michal Hocko To: Ilya Dryomov Cc: Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , stable@vger.kernel.org, Sergey Jerusalimov , Jeff Layton , linux-xfs@vger.kernel.org Subject: Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations Message-ID: <20170329105536.GH27994@dhcp22.suse.cz> References: <20170328122559.966310440@linuxfoundation.org> <20170328122601.905696872@linuxfoundation.org> <20170328124312.GE18241@dhcp22.suse.cz> <20170328133040.GJ18241@dhcp22.suse.cz> <20170329104126.GF27994@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170329104126.GF27994@dhcp22.suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 738 Lines: 26 On Wed 29-03-17 12:41:26, Michal Hocko wrote: [...] > > ceph_con_workfn > > mutex_lock(&con->mutex) # ceph_connection::mutex > > try_write > > ceph_tcp_connect > > sock_create_kern > > GFP_KERNEL allocation > > allocator recurses into XFS, more I/O is issued One more note. So what happens if this is a GFP_NOIO request which cannot make any progress? Your IO thread is blocked on con->mutex as you write below but the above thread cannot proceed as well. So I am _really_ not sure this acutally helps. [...] > > > > rbd_queue_workfn > > ceph_osdc_start_request > > mutex_lock(&osdc->request_mutex); > > ceph_con_send > > mutex_lock(&con->mutex) # deadlock -- Michal Hocko SUSE Labs