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(v: &lock->v, i: 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, v: &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(v: &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(v: &lock->v,
47 old, new: 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

source code of linux/fs/bcachefs/two_state_shared_lock.h