filelock: add new locks_wake_up_waiter() helper

Currently the function that does this takes a struct file_lock, but
__locks_wake_up_blocks() deals with both locks and leases. Currently
this works because both file_lock and file_lease have the file_lock_core
at the beginning of the struct, but it's fragile to rely on that.

Add a new locks_wake_up_waiter() function and call that from
__locks_wake_up_blocks().

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/20250602-filelock-6-16-v1-1-7da5b2c930fd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: jtlayton

fs/locks.c

@@ -712,7 +712,7 @@ static void __locks_wake_up_blocks(struct file_lock_core *blocker)
 		    fl->fl_lmops && fl->fl_lmops->lm_notify)
 			fl->fl_lmops->lm_notify(fl);
 		else
-			locks_wake_up(fl);
+			locks_wake_up_waiter(waiter);
 
 		/*
 		 * The setting of flc_blocker to NULL marks the "done"

include/linux/filelock.h

@@ -175,9 +175,14 @@ static inline bool lock_is_write(struct file_lock *fl)
 	return fl->c.flc_type == F_WRLCK;
 }
 
+static inline void locks_wake_up_waiter(struct file_lock_core *flc)
+{
+	wake_up(&flc->flc_wait);
+}
+
 static inline void locks_wake_up(struct file_lock *fl)
 {
-	wake_up(&fl->c.flc_wait);
+	locks_wake_up_waiter(&fl->c);
 }
 
 static inline bool locks_can_async_lock(const struct file_operations *fops)