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Date: Wed, 29 Mar 2017 12:55:36 +0200 From: Michal Hocko <mhocko@...nel.org> To: Ilya Dryomov <idryomov@...il.com> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, stable@...r.kernel.org, Sergey Jerusalimov <wintchester@...il.com>, Jeff Layton <jlayton@...hat.com>, linux-xfs@...r.kernel.org Subject: Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations 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
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