lustre/ptlrpc: rq_commit_cb is called for twice

If a ptlrpc_request is already on imp::imp_replay_list, when it's
replayed and replied, after_reply() will call req::rq_commit_cb
for the request, then call it again in ptlrpc_free_committed.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-on: http://review.whamcloud.com/8815
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3618
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/client.c

@@ -1316,7 +1316,11 @@ static int after_reply(struct ptlrpc_request *req)
 			/** version recovery */
 			ptlrpc_save_versions(req);
 			ptlrpc_retain_replayable_request(req, imp);
-		} else if (req->rq_commit_cb != NULL) {
+		} else if (req->rq_commit_cb != NULL &&
+			   list_empty(&req->rq_replay_list)) {
+			/* NB: don't call rq_commit_cb if it's already on
+			 * rq_replay_list, ptlrpc_free_committed() will call
+			 * it later, see LU-3618 for details */
 			spin_unlock(&imp->imp_lock);
 			req->rq_commit_cb(req);
 			spin_lock(&imp->imp_lock);