libceph: ceph-msgr workqueue needs a resque worker

commit f9865f0 upstream.

Commit f363e45 ("net/ceph: make ceph_msgr_wq non-reentrant")
effectively removed WQ_MEM_RECLAIM flag from ceph_msgr_wq.  This is
wrong - libceph is very much a memory reclaim path, so restore it.

Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Tested-by: Micha Krause <micha@krausam.de>
Reviewed-by: Sage Weil <sage@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/ceph/messenger.c

@@ -290,7 +290,8 @@ int ceph_msgr_init(void)
 	if (ceph_msgr_slab_init())
 		return -ENOMEM;
 
-	ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
+	ceph_msgr_wq = alloc_workqueue("ceph-msgr",
+				       WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
 	if (ceph_msgr_wq)
 		return 0;