block: elevator: forbid init from changing I/O scheduler

Userspace sets bfq when booting is done, we do not want this to
happen because we use upstreamed cfq by default.

Signed-off-by: Yaroslav Furman <yaro330@gmail.com>
Signed-off-by: UtsavisGreat <utsavbalar1231@gmail.com>

block/elevator.c

@@ -90,6 +90,10 @@ static struct elevator_type *elevator_find(const char *name, bool mq)
 {
 	struct elevator_type *e;
 
+	/* Forbid init from changing I/O scheduler from default */
+	if (!strncmp(current->comm, "init", sizeof("init")))
+		return NULL;
+
 	list_for_each_entry(e, &elv_list, list) {
 		if (!strcmp(e->elevator_name, name) && (mq == e->uses_mq))
 			return e;