Ceph

Hello,
I have a ceph mimic cluster with cephfs.
I create few snapshots (mkdir .snap/test etc...) in different directories. So far so good.
But when I delete the snapshots (rmdir .snap/test etc...) the cluster get in a warn state with :

1. ceph -w
   cluster:
   id: 2fbbf089-a846-4c09-90bc-1dd9bd7af30f
   health: HEALTH_WARN
   3 slow ops, oldest one blocked for 11415 sec, mon.lpnceph01 has slow ops
   ...
   2018-12-06 16:54:56.356518 mon.lpnceph-mon01 [WRN] Health check update: 3 slow ops, oldest one blocked for 11410 sec, mon.lpnceph01 has slow ops (SLOW_OPS)
   2018-12-06 16:55:05.856294 mon.lpnceph-mon01 [WRN] Health check update: 3 slow ops, oldest one blocked for 11415 sec, mon.lpnceph01 has slow ops (SLOW_OPS)
   2018-12-06 16:55:10.856657 mon.lpnceph-mon01 [WRN] Health check update: 3 slow ops, oldest one blocked for 11425 sec, mon.lpnceph01 has slow ops (SLOW_OPS)

It's obviously related to the removal of snapshots because :

1. ceph daemon mon.lpnceph01 ops {
   "ops": [ {
   "description": "remove_snaps({28=[3,4]} v0)",
   "initiated_at": "2018-12-06 13:44:41.396039",
   "age": 14549.148016,
   "duration": 14549.148028,
   "type_data": {
   "events": [ {
   "time": "2018-12-06 13:44:41.396039",
   "event": "initiated"
   }, {
   "time": "2018-12-06 13:44:41.396039",
   "event": "header_read"
   }, {
   "time": "2018-12-06 13:44:41.396042",
   "event": "throttled"
   }, {
   "time": "2018-12-06 13:44:41.396089",
   "event": "all_read"
   }, {
   "time": "2018-12-06 13:44:41.396186",
   "event": "dispatched"
   }, {
   "time": "2018-12-06 13:44:41.396190",
   "event": "mon:_ms_dispatch"
   }, {
   "time": "2018-12-06 13:44:41.396191",
   "event": "mon:dispatch_op"
   }, {
   "time": "2018-12-06 13:44:41.396192",
   "event": "psvc:dispatch"
   }, {
   "time": "2018-12-06 13:44:41.396205",
   "event": "osdmap:preprocess_query"
   }, {
   "time": "2018-12-06 13:44:41.396214",
   "event": "osdmap:preprocess_remove_snaps"
   }, {
   "time": "2018-12-06 13:44:41.396220",
   "event": "forward_request_leader"
   }, {
   "time": "2018-12-06 13:44:41.396258",
   "event": "forwarded"
   }
   ],
   "info": {
   "seq": 250448,
   "src_is_mon": false,
   "source": "mds.0 xxx.xxx.xxx.xxx:6800/2790459226",
   "forwarded_to_leader": true
   }
   }
   },
   ...

I tryed to add in ceph.conf the lines :
[osd]
osd snap trim sleep = 0.6

as suggested in http://lists.ceph.com/pipermail/ceph-users-ceph.com/2018-November/031227.html
but it doesn't solve the problem.

I had to restart the service :
systemctl restart ceph-mon@lpnceph01.service

to get the cluster back to healty status.