// SPDX-License-Identifier: GPL-2.0
#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(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 pin_kill(struct fs_pin *p)
{
        wait_queue_entry_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.entry)))
                        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 = READ_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 = READ_ONCE(p->first);
                if (!q) {
                        rcu_read_unlock();
                        break;
                }
                pin_kill(hlist_entry(q, struct fs_pin, s_list));
        }
}