rcutorture: Add ability to test srcu_read_{,un}lock_fast()

This commit permits rcutorture to test srcu_read_{,un}lock_fast(), which
is specified by the rcutorture.reader_flavor=0x8 kernel boot parameter.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

kernel/rcu/rcutorture.c

@@ -677,6 +677,7 @@ static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
 static int srcu_torture_read_lock(void)
 {
 	int idx;
+	struct srcu_ctr __percpu *scp;
 	int ret = 0;
 
 	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
@@ -694,6 +695,12 @@ static int srcu_torture_read_lock(void)
 		WARN_ON_ONCE(idx & ~0x1);
 		ret += idx << 2;
 	}
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+		scp = srcu_read_lock_fast(srcu_ctlp);
+		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
+		WARN_ON_ONCE(idx & ~0x1);
+		ret += idx << 3;
+	}
 	return ret;
 }
 
@@ -719,6 +726,8 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 static void srcu_torture_read_unlock(int idx)
 {
 	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+		srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
 	if (reader_flavor & SRCU_READ_FLAVOR_LITE)
 		srcu_read_unlock_lite(srcu_ctlp, (idx & 0x4) >> 2);
 	if (reader_flavor & SRCU_READ_FLAVOR_NMI)