#include <linux/fs.h>
  #include <linux/slab.h>
  #include <linux/fs_pin.h>

  #include "internal.h"

  #include "mount.h"
  
  static void pin_free_rcu(struct rcu_head *head)
  {
  	kfree(container_of(head, struct fs_pin, rcu));
  }
  
  static DEFINE_SPINLOCK(pin_lock);
  
  void pin_put(struct fs_pin *p)
  {
  	if (atomic_long_dec_and_test(&p->count))
  		call_rcu(&p->rcu, pin_free_rcu);
  }
  
  void pin_remove(struct fs_pin *pin)
  {
  	spin_lock(&pin_lock);
  	hlist_del(&pin->m_list);
  	hlist_del(&pin->s_list);
  	spin_unlock(&pin_lock);
  }
  
  void pin_insert(struct fs_pin *pin, struct vfsmount *m)
  {
  	spin_lock(&pin_lock);
  	hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins);
  	hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
  	spin_unlock(&pin_lock);
  }

  void mnt_pin_kill(struct mount *m)

  {
  	while (1) {
  		struct hlist_node *p;
  		struct fs_pin *pin;
  		rcu_read_lock();

  		p = ACCESS_ONCE(m->mnt_pins.first);

  		if (!p) {
  			rcu_read_unlock();
  			break;
  		}
  		pin = hlist_entry(p, struct fs_pin, m_list);
  		if (!atomic_long_inc_not_zero(&pin->count)) {
  			rcu_read_unlock();
  			cpu_relax();
  			continue;
  		}
  		rcu_read_unlock();
  		pin->kill(pin);
  	}
  }

  void sb_pin_kill(struct super_block *sb)

  {
  	while (1) {
  		struct hlist_node *p;
  		struct fs_pin *pin;
  		rcu_read_lock();

  		p = ACCESS_ONCE(sb->s_pins.first);

  		if (!p) {
  			rcu_read_unlock();
  			break;
  		}
  		pin = hlist_entry(p, struct fs_pin, s_list);
  		if (!atomic_long_inc_not_zero(&pin->count)) {
  			rcu_read_unlock();
  			cpu_relax();
  			continue;
  		}
  		rcu_read_unlock();
  		pin->kill(pin);
  	}
  }