kfence: test: fail fast if disabled at boot

Fail kfence_test fast if KFENCE was disabled at boot, instead of each test
case trying several seconds to allocate from KFENCE and failing.  KUnit
will fail all test cases if kunit_suite::init returns an error.

Even if KFENCE was disabled, we still want the test to fail, so that CI
systems that parse KUnit output will alert on KFENCE being disabled
(accidentally or otherwise).

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Marco Elver <[email protected]>
Reported-by: Kefeng Wang <[email protected]>
Tested-by: Kefeng Wang <[email protected]>
Acked-by: Alexander Potapenko <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: melver

mm/kfence/kfence_test.c

@@ -789,6 +789,9 @@ static int test_init(struct kunit *test)
 	unsigned long flags;
 	int i;
 
+	if (!__kfence_pool)
+		return -EINVAL;
+
 	spin_lock_irqsave(&observed.lock, flags);
 	for (i = 0; i < ARRAY_SIZE(observed.lines); i++)
 		observed.lines[i][0] = '\0';