RDS: Track transports via an array, not a list

Now that transports can be loaded in arbitrary order,
it is important for rds_trans_get_preferred() to look
for them in a particular order, instead of walking the list
until it finds a transport that works for a given address.
Now, each transport registers for a specific transport slot,
and these are ordered so that preferred transports come first,
and then if they are not loaded, other transports are queried.

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

5 files changed, 28 insertions, 10 deletions

diff --git a/net/rds/ib.c b/net/rds/ib.c
index 868559ac42d7..536ebe5d3f6b 100644
--- a/net/rds/ib.c
+++ b/net/rds/ib.c
@@ -282,6 +282,7 @@ struct rds_transport rds_ib_transport = {
         .flush_mrs              = rds_ib_flush_mrs,
         .t_owner                = THIS_MODULE,
         .t_name                 = "infiniband",
+        .t_type                 = RDS_TRANS_IB
 };
 
 int __init rds_ib_init(void)
diff --git a/net/rds/iw.c b/net/rds/iw.c
index f5e9a29a80a7..db224f7c2937 100644
--- a/net/rds/iw.c
+++ b/net/rds/iw.c
@@ -284,6 +284,7 @@ struct rds_transport rds_iw_transport = {
         .flush_mrs              = rds_iw_flush_mrs,
         .t_owner                = THIS_MODULE,
         .t_name                 = "iwarp",
+        .t_type                 = RDS_TRANS_IWARP,
         .t_prefer_loopback      = 1,
 };
 
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 290566c69d28..85d6f897ecc7 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -311,11 +311,17 @@ struct rds_notifier {
  *                 flag and header.
  */
 
+#define RDS_TRANS_IB    0
+#define RDS_TRANS_IWARP 1
+#define RDS_TRANS_TCP   2
+#define RDS_TRANS_COUNT 3
+
 struct rds_transport {
         char                    t_name[TRANSNAMSIZ];
         struct list_head        t_item;
         struct module           *t_owner;
         unsigned int            t_prefer_loopback:1;
+        unsigned int            t_type;
 
         int (*laddr_check)(__be32 addr);
         int (*conn_alloc)(struct rds_connection *conn, gfp_t gfp);
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index e0ac9009db1a..b5198aee45d3 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -271,6 +271,7 @@ struct rds_transport rds_tcp_transport = {
         .exit                   = rds_tcp_exit,
         .t_owner                = THIS_MODULE,
         .t_name                 = "tcp",
+        .t_type                 = RDS_TRANS_TCP,
         .t_prefer_loopback      = 1,
 };
 
diff --git a/net/rds/transport.c b/net/rds/transport.c
index 56a530996a4a..7e1067901353 100644
--- a/net/rds/transport.c
+++ b/net/rds/transport.c
@@ -37,7 +37,7 @@
 #include "rds.h"
 #include "loop.h"
 
-static LIST_HEAD(rds_transports);
+static struct rds_transport *transports[RDS_TRANS_COUNT];
 static DECLARE_RWSEM(rds_trans_sem);
 
 int rds_trans_register(struct rds_transport *trans)
@@ -46,8 +46,13 @@ int rds_trans_register(struct rds_transport *trans)
 
         down_write(&rds_trans_sem);
 
-        list_add_tail(&trans->t_item, &rds_transports);
-        printk(KERN_INFO "Registered RDS/%s transport\n", trans->t_name);
+        if (transports[trans->t_type])
+                printk(KERN_ERR "RDS Transport type %d already registered\n",
+                        trans->t_type);
+        else {
+                transports[trans->t_type] = trans;
+                printk(KERN_INFO "Registered RDS/%s transport\n", trans->t_name);
+        }
 
         up_write(&rds_trans_sem);
 
@@ -59,7 +64,7 @@ void rds_trans_unregister(struct rds_transport *trans)
 {
         down_write(&rds_trans_sem);
 
-        list_del_init(&trans->t_item);
+        transports[trans->t_type] = NULL;
         printk(KERN_INFO "Unregistered RDS/%s transport\n", trans->t_name);
 
         up_write(&rds_trans_sem);
@@ -68,16 +73,17 @@ EXPORT_SYMBOL_GPL(rds_trans_unregister);
 
 struct rds_transport *rds_trans_get_preferred(__be32 addr)
 {
-        struct rds_transport *trans;
         struct rds_transport *ret = NULL;
+        int i;
 
         if (IN_LOOPBACK(ntohl(addr)))
                 return &rds_loop_transport;
 
         down_read(&rds_trans_sem);
-        list_for_each_entry(trans, &rds_transports, t_item) {
-                if (trans->laddr_check(addr) == 0) {
-                        ret = trans;
+        for (i = 0; i < RDS_TRANS_COUNT; i++)
+        {
+                if (transports[i] && (transports[i]->laddr_check(addr) == 0)) {
+                        ret = transports[i];
                         break;
                 }
         }
@@ -99,12 +105,15 @@ unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
         struct rds_transport *trans;
         unsigned int total = 0;
         unsigned int part;
+        int i;
 
         rds_info_iter_unmap(iter);
         down_read(&rds_trans_sem);
 
-        list_for_each_entry(trans, &rds_transports, t_item) {
-                if (trans->stats_info_copy == NULL)
+        for (i = 0; i < RDS_TRANS_COUNT; i++)
+        {
+                trans = transports[i];
+                if (!trans || !trans->stats_info_copy)
                         continue;
 
                 part = trans->stats_info_copy(iter, avail);