null_blk: fix return value from null_add_dev()

jira LE-1907
Rebuild_History Non-Buildable kernel-4.18.0-553.16.1.el8_10
commit-author Chaitanya Kulkarni <[email protected]>
commit a75110c

The function nullb_device_power_store() returns -ENOMEM when
null_add_dev() fails. null_add_dev() can fail with return value
other than -ENOMEM such as -EINVAL when Zoned Block Device option
is used, see :

nullb_device_power_store()
 null_add_dev()
  null_init_zoned_dev()
	return -EINVAL;

When trying to load the module having -ENOMEM value returned on the
command line creates confusion when pleanty of memory is free on the
machine.

Instead of hardcoding -ENOMEM return the value of null_add_dev()
function.

	Signed-off-by: Chaitanya Kulkarni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
	Signed-off-by: Jens Axboe <[email protected]>
(cherry picked from commit a75110c)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

drivers/block/null_blk_main.c

@@ -414,9 +414,10 @@ static ssize_t nullb_device_power_store(struct config_item *item,
 	if (!dev->power && newp) {
 		if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
 			return count;
-		if (null_add_dev(dev)) {
+		ret = null_add_dev(dev);
+		if (ret) {
 			clear_bit(NULLB_DEV_FL_UP, &dev->flags);
-			return -ENOMEM;
+			return ret;
 		}
 
 		set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);