locks: New ops in lock_manager_operations for get/put owner

NFSD or other lockmanager may increase the owner's reference,
so adds two new options for copying and releasing owner.

v5: change order from 2/6 to 3/6
v4: rename lm_copy_owner/lm_release_owner to lm_get_owner/lm_put_owner
Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>

fs/locks.c

@@ -230,8 +230,12 @@ void locks_release_private(struct file_lock *fl)
 			fl->fl_ops->fl_release_private(fl);
 		fl->fl_ops = NULL;
 	}
-	fl->fl_lmops = NULL;
 
+	if (fl->fl_lmops) {
+		if (fl->fl_lmops->lm_put_owner)
+			fl->fl_lmops->lm_put_owner(fl);
+		fl->fl_lmops = NULL;
+	}
 }
 EXPORT_SYMBOL_GPL(locks_release_private);
 
@@ -274,8 +278,12 @@ static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
 			fl->fl_ops->fl_copy_lock(new, fl);
 		new->fl_ops = fl->fl_ops;
 	}
-	if (fl->fl_lmops)
+
+	if (fl->fl_lmops) {
+		if (fl->fl_lmops->lm_get_owner)
+			fl->fl_lmops->lm_get_owner(new, fl);
 		new->fl_lmops = fl->fl_lmops;
+	}
 }
 
 /*

include/linux/fs.h

@@ -868,6 +868,8 @@ struct file_lock_operations {
 struct lock_manager_operations {
 	int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
 	unsigned long (*lm_owner_key)(struct file_lock *);
+	void (*lm_get_owner)(struct file_lock *, struct file_lock *);
+	void (*lm_put_owner)(struct file_lock *);
 	void (*lm_notify)(struct file_lock *);	/* unblock callback */
 	int (*lm_grant)(struct file_lock *, int);
 	void (*lm_break)(struct file_lock *);