root/include/linux/fs_pin.h

#include <linux/fs.h>

struct fs_pin {
        atomic_long_t           count;
        union {
                struct {
                        struct hlist_node       s_list;
                        struct hlist_node       m_list;
                };
                struct rcu_head rcu;
        };
        void (*kill)(struct fs_pin *);
};

void pin_put(struct fs_pin *);
void pin_remove(struct fs_pin *);
void pin_insert(struct fs_pin *, struct vfsmount *);