locking/lockdep: Avoid creating new name string literals in lockdep_set_subclass()

Syzbot reports a problem that a warning will be triggered while
searching a lock class in look_up_lock_class().

The cause of the issue is that a new name is created and used by
lockdep_set_subclass() instead of using the existing one. This results
in a lock instance has a different name pointer than previous registered
one stored in lock class, and WARN_ONCE() is triggered because of that
in look_up_lock_class().

To fix this, change lockdep_set_subclass() to use the existing name
instead of a new one. Hence, no new name will be created by
lockdep_set_subclass(). Hence, the warning is avoided.

[boqun: Reword the commit log to state the correct issue]

Reported-by: <[email protected]>
Fixes: de8f5e4 ("lockdep: Introduce wait-type checks")
Cc: [email protected]
Signed-off-by: Ahmed Ehab <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/

Author: botta633

include/linux/lockdep.h

@@ -173,7 +173,7 @@ static inline void lockdep_init_map(struct lockdep_map *lock, const char *name,
 			      (lock)->dep_map.lock_type)
 
 #define lockdep_set_subclass(lock, sub)					\
-	lockdep_init_map_type(&(lock)->dep_map, #lock, (lock)->dep_map.key, sub,\
+	lockdep_init_map_type(&(lock)->dep_map, (lock)->dep_map.name, (lock)->dep_map.key, sub,\
 			      (lock)->dep_map.wait_type_inner,		\
 			      (lock)->dep_map.wait_type_outer,		\
 			      (lock)->dep_map.lock_type)