fs/fs_pin.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/fs.h>
   3 #include <linux/sched.h>
   4 #include <linux/slab.h>
   5 #include "internal.h"
   6 #include "mount.h"
   7
   8 static DEFINE_SPINLOCK(pin_lock);
   9
  10 void pin_remove(struct fs_pin *pin)
  11 {
  12         spin_lock(&pin_lock);
  13         hlist_del_init(&pin->m_list);
  14         hlist_del_init(&pin->s_list);
  15         spin_unlock(&pin_lock);
  16         spin_lock_irq(&pin->wait.lock);
  17         pin->done = 1;
  18         wake_up_locked(&pin->wait);
  19         spin_unlock_irq(&pin->wait.lock);
  20 }
  21
  22 void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p)
  23 {
  24         spin_lock(&pin_lock);
  25         if (p)
  26                 hlist_add_head(&pin->s_list, p);
  27         hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
  28         spin_unlock(&pin_lock);
  29 }
  30
  31 void pin_insert(struct fs_pin *pin, struct vfsmount *m)
  32 {
  33         pin_insert_group(pin, m, &m->mnt_sb->s_pins);
  34 }
  35
  36 void pin_kill(struct fs_pin *p)
  37 {
  38         wait_queue_entry_t wait;
  39
  40         if (!p) {
  41                 rcu_read_unlock();
  42                 return;
  43         }
  44         init_wait(&wait);
  45         spin_lock_irq(&p->wait.lock);
  46         if (likely(!p->done)) {
  47                 p->done = -1;
  48                 spin_unlock_irq(&p->wait.lock);
  49                 rcu_read_unlock();
  50                 p->kill(p);
  51                 return;
  52         }
  53         if (p->done > 0) {
  54                 spin_unlock_irq(&p->wait.lock);
  55                 rcu_read_unlock();
  56                 return;
  57         }
  58         __add_wait_queue(&p->wait, &wait);
  59         while (1) {
  60                 set_current_state(TASK_UNINTERRUPTIBLE);
  61                 spin_unlock_irq(&p->wait.lock);
  62                 rcu_read_unlock();
  63                 schedule();
  64                 rcu_read_lock();
  65                 if (likely(list_empty(&wait.entry)))
  66                         break;
  67                 /* OK, we know p couldn't have been freed yet */
  68                 spin_lock_irq(&p->wait.lock);
  69                 if (p->done > 0) {
  70                         spin_unlock_irq(&p->wait.lock);
  71                         break;
  72                 }
  73         }
  74         rcu_read_unlock();
  75 }
  76
  77 void mnt_pin_kill(struct mount *m)
  78 {
  79         while (1) {
  80                 struct hlist_node *p;
  81                 rcu_read_lock();
  82                 p = READ_ONCE(m->mnt_pins.first);
  83                 if (!p) {
  84                         rcu_read_unlock();
  85                         break;
  86                 }
  87                 pin_kill(hlist_entry(p, struct fs_pin, m_list));
  88         }
  89 }
  90
  91 void group_pin_kill(struct hlist_head *p)
  92 {
  93         while (1) {
  94                 struct hlist_node *q;
  95                 rcu_read_lock();
  96                 q = READ_ONCE(p->first);
  97                 if (!q) {
  98                         rcu_read_unlock();
  99                         break;
 100                 }
 101                 pin_kill(hlist_entry(q, struct fs_pin, s_list));
 102         }
 103 }