Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754500AbdC1NYS (ORCPT ); Tue, 28 Mar 2017 09:24:18 -0400 Received: from mail-vk0-f65.google.com ([209.85.213.65]:35705 "EHLO mail-vk0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753569AbdC1NYP (ORCPT ); Tue, 28 Mar 2017 09:24:15 -0400 MIME-Version: 1.0 In-Reply-To: <20170328124312.GE18241@dhcp22.suse.cz> References: <20170328122559.966310440@linuxfoundation.org> <20170328122601.905696872@linuxfoundation.org> <20170328124312.GE18241@dhcp22.suse.cz> From: Ilya Dryomov Date: Tue, 28 Mar 2017 15:23:58 +0200 Message-ID: Subject: Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations To: Michal Hocko Cc: Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , stable@vger.kernel.org, Sergey Jerusalimov , Jeff Layton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 898 Lines: 22 On Tue, Mar 28, 2017 at 2:43 PM, Michal Hocko wrote: > On Tue 28-03-17 14:30:45, Greg KH wrote: >> 4.4-stable review patch. If anyone has any objections, please let me know. > > I haven't seen the original patch but the changelog makes me worried. > How exactly this is a problem? Where do we lockup? Does rbd/libceph take > any xfs locks? No, it doesn't. This is just another instance of "using GFP_KERNEL on the writeback path may lead to a deadlock" with nothing extra to it. XFS is writing out data, libceph messenger worker tries to open a socket and recurses back into XFS because the sockfs inode is allocated with GFP_KERNEL. The message with some of the data never goes out and eventually we get a deadlock. I've only included the offending stack trace. I guess I should have stressed that ceph-msgr workqueue is used for reclaim. Thanks, Ilya