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 
pin_remove(struct fs_pin * pin)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 
pin_insert_group(struct fs_pin * pin,struct vfsmount * m,struct hlist_head * p)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 
pin_insert(struct fs_pin * pin,struct vfsmount * m)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 
pin_kill(struct fs_pin * p)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 
mnt_pin_kill(struct mount * m)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 
group_pin_kill(struct hlist_head * p)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 }
104