#include <linux/fs.h>

  #include <linux/sched.h>

  #include <linux/slab.h>

  #include "internal.h"

  #include "mount.h"

  static DEFINE_SPINLOCK(pin_lock);

  void pin_remove(struct fs_pin *pin)
  {
  	spin_lock(&pin_lock);

  	hlist_del_init(&pin->m_list);
  	hlist_del_init(&pin->s_list);

  	spin_unlock(&pin_lock);

  	spin_lock_irq(&pin->wait.lock);
  	pin->done = 1;
  	wake_up_locked(&pin->wait);
  	spin_unlock_irq(&pin->wait.lock);

  }

  void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p)

  {
  	spin_lock(&pin_lock);

  	if (p)
  		hlist_add_head(&pin->s_list, p);

  	hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
  	spin_unlock(&pin_lock);
  }

  void pin_insert(struct fs_pin *pin, struct vfsmount *m)
  {
  	pin_insert_group(pin, m, &m->mnt_sb->s_pins);
  }

  void pin_kill(struct fs_pin *p)
  {
  	wait_queue_t wait;
  
  	if (!p) {
  		rcu_read_unlock();
  		return;
  	}
  	init_wait(&wait);
  	spin_lock_irq(&p->wait.lock);
  	if (likely(!p->done)) {
  		p->done = -1;
  		spin_unlock_irq(&p->wait.lock);
  		rcu_read_unlock();
  		p->kill(p);
  		return;
  	}
  	if (p->done > 0) {
  		spin_unlock_irq(&p->wait.lock);
  		rcu_read_unlock();
  		return;
  	}
  	__add_wait_queue(&p->wait, &wait);
  	while (1) {
  		set_current_state(TASK_UNINTERRUPTIBLE);
  		spin_unlock_irq(&p->wait.lock);
  		rcu_read_unlock();
  		schedule();
  		rcu_read_lock();
  		if (likely(list_empty(&wait.task_list)))
  			break;
  		/* OK, we know p couldn't have been freed yet */
  		spin_lock_irq(&p->wait.lock);
  		if (p->done > 0) {
  			spin_unlock_irq(&p->wait.lock);
  			break;
  		}
  	}
  	rcu_read_unlock();
  }

  void mnt_pin_kill(struct mount *m)

  {
  	while (1) {
  		struct hlist_node *p;

  		rcu_read_lock();

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

  		if (!p) {
  			rcu_read_unlock();
  			break;
  		}

  		pin_kill(hlist_entry(p, struct fs_pin, m_list));

  	}
  }

  void group_pin_kill(struct hlist_head *p)

  {
  	while (1) {

  		struct hlist_node *q;

  		rcu_read_lock();

  		q = ACCESS_ONCE(p->first);
  		if (!q) {

  			rcu_read_unlock();
  			break;
  		}

  		pin_kill(hlist_entry(q, struct fs_pin, s_list));

  	}
  }