1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _BCACHEFS_TWO_STATE_LOCK_H
3#define _BCACHEFS_TWO_STATE_LOCK_H
4
5#include <linux/atomic.h>
6#include <linux/sched.h>
7#include <linux/wait.h>
8
9#include "util.h"
10
11/*
12 * Two-state lock - can be taken for add or block - both states are shared,
13 * like read side of rwsem, but conflict with other state:
14 */
15typedef struct {
16	atomic_long_t		v;
17	wait_queue_head_t	wait;
18} two_state_lock_t;
19
20static inline void two_state_lock_init(two_state_lock_t *lock)
21{
22	atomic_long_set(&lock->v, 0);
23	init_waitqueue_head(&lock->wait);
24}
25
26static inline void bch2_two_state_unlock(two_state_lock_t *lock, int s)
27{
28	long i = s ? 1 : -1;
29
30	EBUG_ON(atomic_long_read(&lock->v) == 0);
31
32	if (atomic_long_sub_return_release(i, &lock->v) == 0)
33		wake_up_all(&lock->wait);
34}
35
36static inline bool bch2_two_state_trylock(two_state_lock_t *lock, int s)
37{
38	long i = s ? 1 : -1;
39	long v = atomic_long_read(&lock->v), old;
40
41	do {
42		old = v;
43
44		if (i > 0 ? v < 0 : v > 0)
45			return false;
46	} while ((v = atomic_long_cmpxchg_acquire(&lock->v,
47					old, old + i)) != old);
48	return true;
49}
50
51void __bch2_two_state_lock(two_state_lock_t *, int);
52
53static inline void bch2_two_state_lock(two_state_lock_t *lock, int s)
54{
55	if (!bch2_two_state_trylock(lock, s))
56		__bch2_two_state_lock(lock, s);
57}
58
59#endif /* _BCACHEFS_TWO_STATE_LOCK_H */
60