IB/core: convert to idr_alloc()

Convert to the much saner new idr interface.

v2: Mike triggered WARN_ON() in idr_preload() because send_mad(),
    which may be used from non-process context, was calling
    idr_preload() unconditionally.  Preload iff @gfp_mask has
    __GFP_WAIT.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Reported-by: "Marciniszyn, Mike" <mike.marciniszyn@intel.com>
Cc: Roland Dreier <roland@kernel.org>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index d789eea..c32eeaa 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -2143,33 +2143,23 @@
 			  unsigned short snum)
 {
 	struct rdma_bind_list *bind_list;
-	int port, ret;
+	int ret;
 
 	bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
 	if (!bind_list)
 		return -ENOMEM;
 
-	do {
-		ret = idr_get_new_above(ps, bind_list, snum, &port);
-	} while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
-
-	if (ret)
-		goto err1;
-
-	if (port != snum) {
-		ret = -EADDRNOTAVAIL;
-		goto err2;
-	}
+	ret = idr_alloc(ps, bind_list, snum, snum + 1, GFP_KERNEL);
+	if (ret < 0)
+		goto err;
 
 	bind_list->ps = ps;
-	bind_list->port = (unsigned short) port;
+	bind_list->port = (unsigned short)ret;
 	cma_bind_port(bind_list, id_priv);
 	return 0;
-err2:
-	idr_remove(ps, port);
-err1:
+err:
 	kfree(bind_list);
-	return ret;
+	return ret == -ENOSPC ? -EADDRNOTAVAIL : ret;
 }
 
 static int cma_alloc_any_port(struct idr *ps, struct rdma_id_private *id_priv)