iser-target: introduce fast memory registration mode (FRWR)

This model was introduced in 00f7ec36 "RDMA/core: Add memory
management extensions support" and works when the IB device
supports the IB_DEVICE_MEM_MGT_EXTENSIONS capability.

Upon creating the isert device, ib_isert will test whether the HCA
supports FRWR. If supported then set the flag and assign
function pointers that handle fast registration and deregistration
of appropriate resources (fast_reg descriptors).

When new connection coming in, ib_isert will check frwr flag and
create frwr resouces, if fail to do it will switch back to
old model of using global dma key and turn off the frwr support.

Registration is done using posting IB_WR_FAST_REG_MR to the QP and
invalidations using posting IB_WR_LOCAL_INV.
Signed-off-by: Vu Pham <vu@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.h

@@ -5,6 +5,7 @@
 #include <rdma/rdma_cm.h>
 
 #define ISERT_RDMA_LISTEN_BACKLOG	10
+#define ISCSI_ISER_SG_TABLESIZE		256
 
 enum isert_desc_type {
 	ISCSI_TX_CONTROL,
@@ -45,16 +46,26 @@ struct iser_tx_desc {
 	struct ib_send_wr send_wr;
 } __packed;
 
+struct fast_reg_descriptor {
+	struct list_head	list;
+	struct ib_mr		*data_mr;
+	struct ib_fast_reg_page_list	*data_frpl;
+	bool			valid;
+};
+
 struct isert_rdma_wr {
 	struct list_head	wr_list;
 	struct isert_cmd	*isert_cmd;
 	enum iser_ib_op_code	iser_ib_op;
 	struct ib_sge		*ib_sge;
+	struct ib_sge		s_ib_sge;
 	int			num_sge;
 	struct scatterlist	*sge;
 	int			send_wr_num;
 	struct ib_send_wr	*send_wr;
+	struct ib_send_wr	s_send_wr;
 	u32			cur_rdma_length;
+	struct fast_reg_descriptor *fr_desc;
 };
 
 struct isert_cmd {
@@ -106,6 +117,10 @@ struct isert_conn {
 	wait_queue_head_t	conn_wait;
 	wait_queue_head_t	conn_wait_comp_err;
 	struct kref		conn_kref;
+	struct list_head	conn_frwr_pool;
+	int			conn_frwr_pool_size;
+	/* lock to protect frwr_pool */
+	spinlock_t		conn_lock;
 };
 
 #define ISERT_MAX_CQ 64
@@ -118,6 +133,7 @@ struct isert_cq_desc {
 };
 
 struct isert_device {
+	int			use_frwr;
 	int			cqs_used;
 	int			refcount;
 	int			cq_active_qps[ISERT_MAX_CQ];
@@ -128,6 +144,7 @@ struct isert_device {
 	struct ib_cq		*dev_tx_cq[ISERT_MAX_CQ];
 	struct isert_cq_desc	*cq_desc;
 	struct list_head	dev_node;
+	struct ib_device_attr	dev_attr;
 	int			(*reg_rdma_mem)(struct iscsi_conn *conn,
 						    struct iscsi_cmd *cmd,
 						    struct isert_rdma_wr *wr);