RDS: Refactor end of __conn_create for readability

Add a comment for what's going on. Remove negative logic.
I find this much easier to understand quickly, although
there are a few lines duplicated.

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

1 files changed, 31 insertions, 17 deletions

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 605fe3f60de3..b420a20d84fd 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -126,7 +126,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
                                        struct rds_transport *trans, gfp_t gfp,
                                        int is_outgoing)
 {
-        struct rds_connection *conn, *tmp, *parent = NULL;
+        struct rds_connection *conn, *parent = NULL;
         struct hlist_head *head = rds_conn_bucket(laddr, faddr);
         unsigned long flags;
         int ret;
@@ -210,26 +210,40 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
           trans->t_name ? trans->t_name : "[unknown]",
           is_outgoing ? "(outgoing)" : "");
 
+        /*
+         * Since we ran without holding the conn lock, someone could
+         * have created the same conn (either normal or passive) in the
+         * interim. We check while holding the lock. If we won, we complete
+         * init and return our conn. If we lost, we rollback and return the
+         * other one.
+         */
         spin_lock_irqsave(&rds_conn_lock, flags);
-        if (parent == NULL) {
-                tmp = rds_conn_lookup(head, laddr, faddr, trans);
-                if (tmp == NULL)
-                        hlist_add_head(&conn->c_hash_node, head);
-        } else {
-                tmp = parent->c_passive;
-                if (!tmp)
+        if (parent) {
+                /* Creating passive conn */
+                if (parent->c_passive) {
+                        trans->conn_free(conn->c_transport_data);
+                        kmem_cache_free(rds_conn_slab, conn);
+                        conn = parent->c_passive;
+                } else {
                         parent->c_passive = conn;
-        }
-
-        if (tmp) {
-                trans->conn_free(conn->c_transport_data);
-                kmem_cache_free(rds_conn_slab, conn);
-                conn = tmp;
+                        rds_cong_add_conn(conn);
+                        rds_conn_count++;
+                }
         } else {
-                rds_cong_add_conn(conn);
-                rds_conn_count++;
+                /* Creating normal conn */
+                struct rds_connection *found;
+
+                found = rds_conn_lookup(head, laddr, faddr, trans);
+                if (found) {
+                        trans->conn_free(conn->c_transport_data);
+                        kmem_cache_free(rds_conn_slab, conn);
+                        conn = found;
+                } else {
+                        hlist_add_head(&conn->c_hash_node, head);
+                        rds_cong_add_conn(conn);
+                        rds_conn_count++;
+                }
         }
-
         spin_unlock_irqrestore(&rds_conn_lock, flags);
 
 out: