centralize killing dentry from shrink list

new helper unifying identical bits of shrink_dentry_list() and
shring_dcache_for_umount()
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/dcache.c

@@ -1174,10 +1174,18 @@ static bool shrink_lock_dentry(struct dentry *dentry)
 	return false;
 }
 
+static inline void shrink_kill(struct dentry *victim, struct list_head *list)
+{
+	struct dentry *parent = victim->d_parent;
+	if (parent != victim)
+		__dput_to_list(parent, list);
+	__dentry_kill(victim);
+}
+
 void shrink_dentry_list(struct list_head *list)
 {
 	while (!list_empty(list)) {
-		struct dentry *dentry, *parent;
+		struct dentry *dentry;
 
 		dentry = list_entry(list->prev, struct dentry, d_lru);
 		spin_lock(&dentry->d_lock);
@@ -1195,10 +1203,7 @@ void shrink_dentry_list(struct list_head *list)
 		}
 		rcu_read_unlock();
 		d_shrink_del(dentry);
-		parent = dentry->d_parent;
-		if (parent != dentry)
-			__dput_to_list(parent, list);
-		__dentry_kill(dentry);
+		shrink_kill(dentry, list);
 	}
 }
 
@@ -1629,17 +1634,13 @@ void shrink_dcache_parent(struct dentry *parent)
 		data.victim = NULL;
 		d_walk(parent, &data, select_collect2);
 		if (data.victim) {
-			struct dentry *parent;
 			spin_lock(&data.victim->d_lock);
 			if (!shrink_lock_dentry(data.victim)) {
 				spin_unlock(&data.victim->d_lock);
 				rcu_read_unlock();
 			} else {
 				rcu_read_unlock();
-				parent = data.victim->d_parent;
-				if (parent != data.victim)
-					__dput_to_list(parent, &data.dispose);
-				__dentry_kill(data.victim);
+				shrink_kill(data.victim, &data.dispose);
 			}
 		}
 		if (!list_empty(&data.dispose))