lib/fault-inject.c: use correct check for interrupts

in_interrupt() also returns true when bh is disabled in task context.
That's not what fail_task() wants to check.  Use the new in_task()
predicate that does the right thing.

Link: http://lkml.kernel.org/r/20170321091805.140676-1-dvyukov@google.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/fault-inject.c

@@ -56,7 +56,7 @@ static void fail_dump(struct fault_attr *attr)
 
 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
 {
-	return !in_interrupt() && task->make_it_fail;
+	return in_task() && task->make_it_fail;
 }
 
 #define MAX_STACK_TRACE_DEPTH 32