RDS: Add GET_MR_FOR_DEST sockopt

RDS currently supports a GET_MR sockopt to establish a
memory region (MR) for a chunk of memory. However, the fastreg
method ties a MR to a particular destination. The GET_MR_FOR_DEST
sockopt allows the remote machine to be specified, and thus
support for fastreg (aka FRWRs).

Note that this patch does *not* do all of this - it simply
implements the new sockopt in terms of the old one, so applications
can begin to use the new sockopt in preparation for cutover to
FRWRs.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 28 insertions, 0 deletions

diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index a202e5b36079..2b978dc6e75d 100644
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -265,6 +265,9 @@ static int rds_setsockopt(struct socket *sock, int level, int optname,
         case RDS_GET_MR:
                 ret = rds_get_mr(rs, optval, optlen);
                 break;
+        case RDS_GET_MR_FOR_DEST:
+                ret = rds_get_mr_for_dest(rs, optval, optlen);
+                break;
         case RDS_FREE_MR:
                 ret = rds_free_mr(rs, optval, optlen);
                 break;
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 8dc83d2caa58..971b5a668458 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -317,6 +317,30 @@ int rds_get_mr(struct rds_sock *rs, char __user *optval, int optlen)
         return __rds_rdma_map(rs, &args, NULL, NULL);
 }
 
+int rds_get_mr_for_dest(struct rds_sock *rs, char __user *optval, int optlen)
+{
+        struct rds_get_mr_for_dest_args args;
+        struct rds_get_mr_args new_args;
+
+        if (optlen != sizeof(struct rds_get_mr_for_dest_args))
+                return -EINVAL;
+
+        if (copy_from_user(&args, (struct rds_get_mr_for_dest_args __user *)optval,
+                           sizeof(struct rds_get_mr_for_dest_args)))
+                return -EFAULT;
+
+        /*
+         * Initially, just behave like get_mr().
+         * TODO: Implement get_mr as wrapper around this
+         *       and deprecate it.
+         */
+        new_args.vec = args.vec;
+        new_args.cookie_addr = args.cookie_addr;
+        new_args.flags = args.flags;
+
+        return __rds_rdma_map(rs, &new_args, NULL, NULL);
+}
+
 /*
  * Free the MR indicated by the given R_Key
  */
diff --git a/net/rds/rdma.h b/net/rds/rdma.h
index 425512098b0b..909c39835a5d 100644
--- a/net/rds/rdma.h
+++ b/net/rds/rdma.h
@@ -61,6 +61,7 @@ static inline u32 rds_rdma_cookie_offset(rds_rdma_cookie_t cookie)
 }
 
 int rds_get_mr(struct rds_sock *rs, char __user *optval, int optlen);
+int rds_get_mr_for_dest(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,