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SubjectRe: [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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