RDS: RDMA support

Some transports may support RDMA features. This handles the
non-transport-specific parts, like pinning user pages and
tracking mapped regions.
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/rdma.h

+#ifndef _RDS_RDMA_H
+#define _RDS_RDMA_H
+
+#include <linux/rbtree.h>
+#include <linux/spinlock.h>
+#include <linux/scatterlist.h>
+
+#include "rds.h"
+
+struct rds_mr {
+	struct rb_node		r_rb_node;
+	atomic_t		r_refcount;
+	u32			r_key;
+
+	/* A copy of the creation flags */
+	unsigned int		r_use_once:1;
+	unsigned int		r_invalidate:1;
+	unsigned int		r_write:1;
+
+	/* This is for RDS_MR_DEAD.
+	 * It would be nice & consistent to make this part of the above
+	 * bit field here, but we need to use test_and_set_bit.
+	 */
+	unsigned long		r_state;
+	struct rds_sock		*r_sock; /* back pointer to the socket that owns us */
+	struct rds_transport	*r_trans;
+	void			*r_trans_private;
+};
+
+/* Flags for mr->r_state */
+#define RDS_MR_DEAD		0
+
+struct rds_rdma_op {
+	u32			r_key;
+	u64			r_remote_addr;
+	unsigned int		r_write:1;
+	unsigned int		r_fence:1;
+	unsigned int		r_notify:1;
+	unsigned int		r_recverr:1;
+	unsigned int		r_mapped:1;
+	struct rds_notifier	*r_notifier;
+	unsigned int		r_bytes;
+	unsigned int		r_nents;
+	unsigned int		r_count;
+	struct scatterlist	r_sg[0];
+};
+
+static inline rds_rdma_cookie_t rds_rdma_make_cookie(u32 r_key, u32 offset)
+{
+	return r_key | (((u64) offset) << 32);
+}
+
+static inline u32 rds_rdma_cookie_key(rds_rdma_cookie_t cookie)
+{
+	return cookie;
+}
+
+static inline u32 rds_rdma_cookie_offset(rds_rdma_cookie_t cookie)
+{
+	return cookie >> 32;
+}
+
+int rds_get_mr(struct rds_sock *rs, char __user *optval, int optlen);
+int rds_free_mr(struct rds_sock *rs, char __user *optval, int optlen);
+void rds_rdma_drop_keys(struct rds_sock *rs);
+int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+int rds_cmsg_rdma_dest(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+int rds_cmsg_rdma_map(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+void rds_rdma_free_op(struct rds_rdma_op *ro);
+void rds_rdma_send_complete(struct rds_message *rm, int);
+
+extern void __rds_put_mr_final(struct rds_mr *mr);
+static inline void rds_mr_put(struct rds_mr *mr)
+{
+	if (atomic_dec_and_test(&mr->r_refcount))
+		__rds_put_mr_final(mr);
+}
+
+#endif