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>

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 6d777069d86d6add74325e970d31541e699e4647..6ae418e81d82f8c772b384c279712d3dbc602f2e 100644 (file)
--- 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)