Re: [PATCH v3 1/3] jump_label: Prevent key->enabled int overflow

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 714ac4c3b556..f2c1aa351d41 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c

@@ -113,11 +113,38 @@ int static_key_count(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_count);
 
-void static_key_slow_inc_cpuslocked(struct static_key *key)
+/***
+ * static_key_fast_inc - adds a user for a static key
+ * @key: static key that must be already enabled
+ *
+ * The caller must make sure that the static key can't get disabled while
+ * in this function. It doesn't patch jump labels, only adds a user to
+ * an already enabled static key.
+ *
+ * Returns true if the increment was done.
+ */
+bool static_key_fast_inc(struct static_key *key)
 {
 	int v, v1;
 
 	STATIC_KEY_CHECK_USE(key);
+	/*
+	 * Negative key->enabled has a special meaning: it sends
+	 * static_key_slow_inc() down the slow path, and it is non-zero
+	 * so it counts as "enabled" in jump_label_update().  Note that
+	 * atomic_inc_unless_negative() checks >= 0, so roll our own.
+	 */
+	for (v = atomic_read(&key->enabled); v > 0 && (v + 1) > 0; v = v1) {
+		v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
+		if (likely(v1 == v))
+			return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(static_key_fast_inc);
+
+bool static_key_slow_inc_cpuslocked(struct static_key *key)
+{
 	lockdep_assert_cpus_held();
 
 	/*

@@ -126,17 +153,9 @@ void static_key_slow_inc_cpuslocked(struct static_key *key)
 	 * jump_label_update() process.  At the same time, however,
 	 * the jump_label_update() call below wants to see
 	 * static_key_enabled(&key) for jumps to be updated properly.
-	 *
-	 * So give a special meaning to negative key->enabled: it sends
-	 * static_key_slow_inc() down the slow path, and it is non-zero
-	 * so it counts as "enabled" in jump_label_update().  Note that
-	 * atomic_inc_unless_negative() checks >= 0, so roll our own.
 	 */
-	for (v = atomic_read(&key->enabled); v > 0; v = v1) {
-		v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
-		if (likely(v1 == v))
-			return;
-	}
+	if (static_key_fast_inc(key))
+		return true;
 
 	jump_label_lock();
 	if (atomic_read(&key->enabled) == 0) {

@@ -148,16 +167,23 @@ void static_key_slow_inc_cpuslocked(struct static_key *key)
 		 */
 		atomic_set_release(&key->enabled, 1);
 	} else {
-		atomic_inc(&key->enabled);
+		if (WARN_ON_ONCE(static_key_fast_inc(key))) {