the-tree/fs/fs_pin.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/fs.h>
0003 #include <linux/sched.h>
0004 #include <linux/slab.h>
0005 #include "internal.h"
0006 #include "mount.h"
0007
0008 static DEFINE_SPINLOCK(pin_lock);
0009
0010 void pin_remove(struct fs_pin *pin)
0011 {
0012     spin_lock(&pin_lock);
0013     hlist_del_init(&pin->m_list);
0014     hlist_del_init(&pin->s_list);
0015     spin_unlock(&pin_lock);
0016     spin_lock_irq(&pin->wait.lock);
0017     pin->done = 1;
0018     wake_up_locked(&pin->wait);
0019     spin_unlock_irq(&pin->wait.lock);
0020 }
0021
0022 void pin_insert(struct fs_pin *pin, struct vfsmount *m)
0023 {
0024     spin_lock(&pin_lock);
0025     hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins);
0026     hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
0027     spin_unlock(&pin_lock);
0028 }
0029
0030 void pin_kill(struct fs_pin *p)
0031 {
0032     wait_queue_entry_t wait;
0033
0034     if (!p) {
0035         rcu_read_unlock();
0036         return;
0037     }
0038     init_wait(&wait);
0039     spin_lock_irq(&p->wait.lock);
0040     if (likely(!p->done)) {
0041         p->done = -1;
0042         spin_unlock_irq(&p->wait.lock);
0043         rcu_read_unlock();
0044         p->kill(p);
0045         return;
0046     }
0047     if (p->done > 0) {
0048         spin_unlock_irq(&p->wait.lock);
0049         rcu_read_unlock();
0050         return;
0051     }
0052     __add_wait_queue(&p->wait, &wait);
0053     while (1) {
0054         set_current_state(TASK_UNINTERRUPTIBLE);
0055         spin_unlock_irq(&p->wait.lock);
0056         rcu_read_unlock();
0057         schedule();
0058         rcu_read_lock();
0059         if (likely(list_empty(&wait.entry)))
0060             break;
0061         /* OK, we know p couldn't have been freed yet */
0062         spin_lock_irq(&p->wait.lock);
0063         if (p->done > 0) {
0064             spin_unlock_irq(&p->wait.lock);
0065             break;
0066         }
0067     }
0068     rcu_read_unlock();
0069 }
0070
0071 void mnt_pin_kill(struct mount *m)
0072 {
0073     while (1) {
0074         struct hlist_node *p;
0075         rcu_read_lock();
0076         p = READ_ONCE(m->mnt_pins.first);
0077         if (!p) {
0078             rcu_read_unlock();
0079             break;
0080         }
0081         pin_kill(hlist_entry(p, struct fs_pin, m_list));
0082     }
0083 }
0084
0085 void group_pin_kill(struct hlist_head *p)
0086 {
0087     while (1) {
0088         struct hlist_node *q;
0089         rcu_read_lock();
0090         q = READ_ONCE(p->first);
0091         if (!q) {
0092             rcu_read_unlock();
0093             break;
0094         }
0095         pin_kill(hlist_entry(q, struct fs_pin, s_list));
0096     }
0097 }