RDMA/uverbs: Use kernel API to allocate uverbs indexes

Replace custom code to allocate indexes to generic kernel API.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/uverbs_main.c

@@ -73,7 +73,7 @@ enum {
 static dev_t dynamic_uverbs_dev;
 static struct class *uverbs_class;
 
-static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
+static DEFINE_IDA(uverbs_ida);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
 				     const char __user *buf, int in_len,
@@ -1268,11 +1268,11 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	rcu_assign_pointer(uverbs_dev->ib_dev, device);
 	uverbs_dev->num_comp_vectors = device->num_comp_vectors;
 
-	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
-	if (devnum >= IB_UVERBS_MAX_DEVICES)
+	devnum = ida_alloc_max(&uverbs_ida, IB_UVERBS_MAX_DEVICES - 1,
+			       GFP_KERNEL);
+	if (devnum < 0)
 		goto err;
 	uverbs_dev->devnum = devnum;
-	set_bit(devnum, dev_map);
 	if (devnum >= IB_UVERBS_NUM_FIXED_MINOR)
 		base = dynamic_uverbs_dev + devnum - IB_UVERBS_NUM_FIXED_MINOR;
 	else
@@ -1296,7 +1296,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	return;
 
 err_uapi:
-	clear_bit(devnum, dev_map);
+	ida_free(&uverbs_ida, devnum);
 err:
 	if (atomic_dec_and_test(&uverbs_dev->refcount))
 		ib_uverbs_comp_dev(uverbs_dev);
@@ -1371,7 +1371,7 @@ static void ib_uverbs_remove_one(struct ib_device *device, void *client_data)
 		return;
 
 	cdev_device_del(&uverbs_dev->cdev, &uverbs_dev->dev);
-	clear_bit(uverbs_dev->devnum, dev_map);
+	ida_free(&uverbs_ida, uverbs_dev->devnum);
 
 	if (device->disassociate_ucontext) {
 		/* We disassociate HW resources and immediately return.