RDMA/cma: Randomize local port allocation

Randomize local port allocation in the way sctp_get_port_local() does.
Update rover at the end of loop since we're likely to pick a valid port
on the first try.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 25 insertions, 45 deletions

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 6d777069d86d..6ae418e81d82 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -79,7 +79,6 @@ static DEFINE_IDR(sdp_ps);
 static DEFINE_IDR(tcp_ps);
 static DEFINE_IDR(udp_ps);
 static DEFINE_IDR(ipoib_ps);
-static int next_port;
 
 struct cma_device {
         struct list_head        list;
@@ -1970,47 +1969,33 @@ err1:
 
 static int cma_alloc_any_port(struct idr *ps, struct rdma_id_private *id_priv)
 {
-        struct rdma_bind_list *bind_list;
-        int port, ret, low, high;
-
-        bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
-        if (!bind_list)
-                return -ENOMEM;
-
-retry:
-        /* FIXME: add proper port randomization per like inet_csk_get_port */
-        do {
-                ret = idr_get_new_above(ps, bind_list, next_port, &port);
-        } while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
-
-        if (ret)
-                goto err1;
+        static unsigned int last_used_port;
+        int low, high, remaining;
+        unsigned int rover;
 
         inet_get_local_port_range(&low, &high);
-        if (port > high) {
-                if (next_port != low) {
-                        idr_remove(ps, port);
-                        next_port = low;
-                        goto retry;
-                }
-                ret = -EADDRNOTAVAIL;
-                goto err2;
+        remaining = (high - low) + 1;
+        rover = net_random() % remaining + low;
+retry:
+        if (last_used_port != rover &&
+            !idr_find(ps, (unsigned short) rover)) {
+                int ret = cma_alloc_port(ps, id_priv, rover);
+                /*
+                 * Remember previously used port number in order to avoid
+                 * re-using same port immediately after it is closed.
+                 */
+                if (!ret)
+                        last_used_port = rover;
+                if (ret != -EADDRNOTAVAIL)
+                        return ret;
         }
-
-        if (port == high)
-                next_port = low;
-        else
-                next_port = port + 1;
-
-        bind_list->ps = ps;
-        bind_list->port = (unsigned short) port;
-        cma_bind_port(bind_list, id_priv);
-        return 0;
-err2:
-        idr_remove(ps, port);
-err1:
-        kfree(bind_list);
-        return ret;
+        if (--remaining) {
+                rover++;
+                if ((rover < low) || (rover > high))
+                        rover = low;
+                goto retry;
+        }
+        return -EADDRNOTAVAIL;
 }
 
 static int cma_use_port(struct idr *ps, struct rdma_id_private *id_priv)
@@ -2995,12 +2980,7 @@ static void cma_remove_one(struct ib_device *device)
 
 static int __init cma_init(void)
 {
-        int ret, low, high, remaining;
-
-        get_random_bytes(&next_port, sizeof next_port);
-        inet_get_local_port_range(&low, &high);
-        remaining = (high - low) + 1;
-        next_port = ((unsigned int) next_port % remaining) + low;
+        int ret;
 
         cma_wq = create_singlethread_workqueue("rdma_cm");
         if (!cma_wq)