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(struct fs_pin *pin, struct vfsmount *m)
  23 {
  24         spin_lock(&pin_lock);
  25         hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins);
  26         hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
  27         spin_unlock(&pin_lock);
  28 }
  29
  30 void pin_kill(struct fs_pin *p)
  31 {
  32         wait_queue_entry_t wait;
  33
  34         if (!p) {
  35                 rcu_read_unlock();
  36                 return;
  37         }
  38         init_wait(&wait);
  39         spin_lock_irq(&p->wait.lock);
  40         if (likely(!p->done)) {
  41                 p->done = -1;
  42                 spin_unlock_irq(&p->wait.lock);
  43                 rcu_read_unlock();
  44                 p->kill(p);
  45                 return;
  46         }
  47         if (p->done > 0) {
  48                 spin_unlock_irq(&p->wait.lock);
  49                 rcu_read_unlock();
  50                 return;
  51         }
  52         __add_wait_queue(&p->wait, &wait);
  53         while (1) {
  54                 set_current_state(TASK_UNINTERRUPTIBLE);
  55                 spin_unlock_irq(&p->wait.lock);
  56                 rcu_read_unlock();
  57                 schedule();
  58                 rcu_read_lock();
  59                 if (likely(list_empty(&wait.entry)))
  60                         break;
  61                 /* OK, we know p couldn't have been freed yet */
  62                 spin_lock_irq(&p->wait.lock);
  63                 if (p->done > 0) {
  64                         spin_unlock_irq(&p->wait.lock);
  65                         break;
  66                 }
  67         }
  68         rcu_read_unlock();
  69 }
  70
  71 void mnt_pin_kill(struct mount *m)
  72 {
  73         while (1) {
  74                 struct hlist_node *p;
  75                 rcu_read_lock();
  76                 p = READ_ONCE(m->mnt_pins.first);
  77                 if (!p) {
  78                         rcu_read_unlock();
  79                         break;
  80                 }
  81                 pin_kill(hlist_entry(p, struct fs_pin, m_list));
  82         }
  83 }
  84
  85 void group_pin_kill(struct hlist_head *p)
  86 {
  87         while (1) {
  88                 struct hlist_node *q;
  89                 rcu_read_lock();
  90                 q = READ_ONCE(p->first);
  91                 if (!q) {
  92                         rcu_read_unlock();
  93                         break;
  94                 }
  95                 pin_kill(hlist_entry(q, struct fs_pin, s_list));
  96         }
  97 }