CIFS: SMBD: Implement RDMA memory registration

Memory registration is used for transferring payload via RDMA read or write.
After I/O is done, memory registrations are recovered and reused. This
process can be time consuming and is done in a work queue.
Signed-off-by: Long Li <longli@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/smbdirect.h

@@ -90,6 +90,29 @@ struct smbd_connection {
 	int receive_credit_target;
 	int fragment_reassembly_remaining;
 
+	/* Memory registrations */
+	/* Maximum number of RDMA read/write outstanding on this connection */
+	int responder_resources;
+	/* Maximum number of SGEs in a RDMA write/read */
+	int max_frmr_depth;
+	/*
+	 * If payload is less than or equal to the threshold,
+	 * use RDMA send/recv to send upper layer I/O.
+	 * If payload is more than the threshold,
+	 * use RDMA read/write through memory registration for I/O.
+	 */
+	int rdma_readwrite_threshold;
+	enum ib_mr_type mr_type;
+	struct list_head mr_list;
+	spinlock_t mr_list_lock;
+	/* The number of available MRs ready for memory registration */
+	atomic_t mr_ready_count;
+	atomic_t mr_used_count;
+	wait_queue_head_t wait_mr;
+	struct work_struct mr_recovery_work;
+	/* Used by transport to wait until all MRs are returned */
+	wait_queue_head_t wait_for_mr_cleanup;
+
 	/* Activity accoutning */
 	/* Pending reqeusts issued from upper layer */
 	int smbd_send_pending;
@@ -262,6 +285,36 @@ void smbd_destroy(struct smbd_connection *info);
 int smbd_recv(struct smbd_connection *info, struct msghdr *msg);
 int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst);
 
+enum mr_state {
+	MR_READY,
+	MR_REGISTERED,
+	MR_INVALIDATED,
+	MR_ERROR
+};
+
+struct smbd_mr {
+	struct smbd_connection	*conn;
+	struct list_head	list;
+	enum mr_state		state;
+	struct ib_mr		*mr;
+	struct scatterlist	*sgl;
+	int			sgl_count;
+	enum dma_data_direction	dir;
+	union {
+		struct ib_reg_wr	wr;
+		struct ib_send_wr	inv_wr;
+	};
+	struct ib_cqe		cqe;
+	bool			need_invalidate;
+	struct completion	invalidate_done;
+};
+
+/* Interfaces to register and deregister MR for RDMA read/write */
+struct smbd_mr *smbd_register_mr(
+	struct smbd_connection *info, struct page *pages[], int num_pages,
+	int tailsz, bool writing, bool need_invalidate);
+int smbd_deregister_mr(struct smbd_mr *mr);
+
 #else
 #define cifs_rdma_enabled(server)	0
 struct smbd_connection {};