+/**
+ * Serializes in-flight MDT-modifying RPC requests to preserve idempotency.
+ *
+ * This mutex is used to implement execute-once semantics on the MDT.
+ * The MDT stores the last transaction ID and result for every client in
+ * its last_rcvd file. If the client doesn't get a reply, it can safely
+ * resend the request and the MDT will reconstruct the reply being aware
+ * that the request has already been executed. Without this lock,
+ * execution status of concurrent in-flight requests would be
+ * overwritten.
+ *
+ * This imlpementation limits the extent to which we can keep a full pipeline
+ * of in-flight requests from a single client. This limitation can be
+ * overcome by allowing multiple slots per client in the last_rcvd file,
+ * see LU-6864.
+ */
+#define OSP_FAKE_RPCL_IT ((void *)0x2c0012bfUL)
+
+static inline void osp_init_rpc_lock(struct osp_device *osp)
+{
+ struct osp_rpc_lock *lck = &osp->opd_rpc_lock;
+
+ mutex_init(&lck->rpcl_mutex);
+ lck->rpcl_fakes = 0;
+}