lib/list_sort: test: improve errors handling

The 'lib_sort()' test does not free memory if it fails, and it makes the
kernel panic if it cannot allocate memory.  This patch fixes the problem.

This patch also changes several small things:
 o use 'list_add()' helper instead of adding manually
 o introduce temporary 'el1' variable to avoid ugly and unreadalbe
   "if" statement
 o make 'head' to be stack variable instead of 'kmalloc()'ed, which
   simplifies code a bit

Overall, this patch is of clean-up type.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Don Mullis <don.mullis@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/list_sort.c

@@ -165,56 +165,67 @@ static int cmp(void *priv, struct list_head *a, struct list_head *b)
 
 static int __init list_sort_test(void)
 {
-	int i, count;
-	struct list_head *head = kmalloc(sizeof(*head), GFP_KERNEL);
-	struct list_head *cur;
+	int i, count = 1, err = -EINVAL;
+	struct debug_el *el;
+	struct list_head *cur, *tmp;
+	LIST_HEAD(head);
 
 	printk(KERN_DEBUG "testing list_sort()\n");
 
-	cur = head;
 	for (i = 0; i < TEST_LIST_LEN; i++) {
-		struct debug_el *el = kmalloc(sizeof(*el), GFP_KERNEL);
-		BUG_ON(!el);
+		el = kmalloc(sizeof(*el), GFP_KERNEL);
+		if (!el) {
+			printk(KERN_ERR "cancel list_sort() testing - cannot "
+					"allocate memory\n");
+			goto exit;
+		}
 		 /* force some equivalencies */
 		el->value = random32() % (TEST_LIST_LEN/3);
 		el->serial = i;
-
-		el->list.prev = cur;
-		cur->next = &el->list;
-		cur = cur->next;
+		list_add_tail(&el->list, &head);
 	}
-	head->prev = cur;
 
-	list_sort(NULL, head, cmp);
+	list_sort(NULL, &head, cmp);
+
+	for (cur = head.next; cur->next != &head; cur = cur->next) {
+		struct debug_el *el1;
+		int cmp_result;
 
-	count = 1;
-	for (cur = head->next; cur->next != head; cur = cur->next) {
-		struct debug_el *el = container_of(cur, struct debug_el, list);
-		int cmp_result = cmp(NULL, cur, cur->next);
 		if (cur->next->prev != cur) {
 			printk(KERN_ERR "list_sort() returned "
 					"a corrupted list!\n");
-			return 1;
-		} else if (cmp_result > 0) {
+			goto exit;
+		}
+
+		cmp_result = cmp(NULL, cur, cur->next);
+		if (cmp_result > 0) {
 			printk(KERN_ERR "list_sort() failed to sort!\n");
-			return 1;
-		} else if (cmp_result == 0 &&
-				el->serial >= container_of(cur->next,
-					struct debug_el, list)->serial) {
+			goto exit;
+		}
+
+		el = container_of(cur, struct debug_el, list);
+		el1 = container_of(cur->next, struct debug_el, list);
+		if (cmp_result == 0 && el->serial >= el1->serial) {
 			printk(KERN_ERR "list_sort() failed to preserve order "
 					"of equivalent elements!\n");
-			return 1;
+			goto exit;
 		}
-		kfree(cur->prev);
 		count++;
 	}
-	kfree(cur);
+
 	if (count != TEST_LIST_LEN) {
 		printk(KERN_ERR "list_sort() returned list of "
 				"different length!\n");
-		return 1;
+		goto exit;
+	}
+
+	err = 0;
+exit:
+	list_for_each_safe(cur, tmp, &head) {
+		list_del(cur);
+		kfree(container_of(cur, struct debug_el, list));
 	}
-	return 0;
+	return err;
 }
 module_init(list_sort_test);
 #endif /* CONFIG_TEST_LIST_SORT */