idr-test: Convert ida_check_nomem to new API

We can't move this test to kernel space because there's no way to
force kmalloc to fail.  But we can use the new API and check this
works when the test is in userspace.
Signed-off-by: Matthew Wilcox <willy@infradead.org>

tools/testing/radix-tree/idr-test.c

@@ -320,19 +320,20 @@ void ida_dump(struct ida *);
 
 /*
  * Check that we get the correct error when we run out of memory doing
- * allocations.  To ensure we run out of memory, just "forget" to preload.
+ * allocations.  In userspace, GFP_NOWAIT will always fail an allocation.
  * The first test is for not having a bitmap available, and the second test
  * is for not being able to allocate a level of the radix tree.
  */
 void ida_check_nomem(void)
 {
 	DEFINE_IDA(ida);
-	int id, err;
+	int id;
 
-	err = ida_get_new_above(&ida, 256, &id);
-	assert(err == -EAGAIN);
-	err = ida_get_new_above(&ida, 1UL << 30, &id);
-	assert(err == -EAGAIN);
+	id = ida_alloc_min(&ida, 256, GFP_NOWAIT);
+	IDA_BUG_ON(&ida, id != -ENOMEM);
+	id = ida_alloc_min(&ida, 1UL << 30, GFP_NOWAIT);
+	IDA_BUG_ON(&ida, id != -ENOMEM);
+	IDA_BUG_ON(&ida, !ida_is_empty(&ida));
 }
 
 /*