1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_PERCPU_COUNTER_H
3 #define _LINUX_PERCPU_COUNTER_H
4 /*
5 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
6 *
7 * WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
8 */
9
10 #include <linux/spinlock.h>
11 #include <linux/smp.h>
12 #include <linux/list.h>
13 #include <linux/threads.h>
14 #include <linux/percpu.h>
15 #include <linux/types.h>
16 #include <linux/gfp.h>
17
18 #ifdef CONFIG_SMP
19
20 struct percpu_counter {
21 raw_spinlock_t lock;
22 s64 count;
23 #ifdef CONFIG_HOTPLUG_CPU
24 struct list_head list; /* All percpu_counters are on a list */
25 #endif
26 s32 __percpu *counters;
27 };
28
29 extern int percpu_counter_batch;
30
31 int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp,
32 struct lock_class_key *key);
33
34 #define percpu_counter_init(fbc, value, gfp) \
35 ({ \
36 static struct lock_class_key __key; \
37 \
38 __percpu_counter_init(fbc, value, gfp, &__key); \
39 })
40
41 void percpu_counter_destroy(struct percpu_counter *fbc);
42 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
43 void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
44 s32 batch);
45 s64 __percpu_counter_sum(struct percpu_counter *fbc);
46 int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
47 void percpu_counter_sync(struct percpu_counter *fbc);
48
percpu_counter_compare(struct percpu_counter * fbc,s64 rhs)49 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
50 {
51 return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
52 }
53
percpu_counter_add(struct percpu_counter * fbc,s64 amount)54 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
55 {
56 percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
57 }
58
percpu_counter_sum_positive(struct percpu_counter * fbc)59 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
60 {
61 s64 ret = __percpu_counter_sum(fbc);
62 return ret < 0 ? 0 : ret;
63 }
64
percpu_counter_sum(struct percpu_counter * fbc)65 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
66 {
67 return __percpu_counter_sum(fbc);
68 }
69
percpu_counter_read(struct percpu_counter * fbc)70 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
71 {
72 return fbc->count;
73 }
74
75 /*
76 * It is possible for the percpu_counter_read() to return a small negative
77 * number for some counter which should never be negative.
78 *
79 */
percpu_counter_read_positive(struct percpu_counter * fbc)80 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
81 {
82 /* Prevent reloads of fbc->count */
83 s64 ret = READ_ONCE(fbc->count);
84
85 if (ret >= 0)
86 return ret;
87 return 0;
88 }
89
percpu_counter_initialized(struct percpu_counter * fbc)90 static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
91 {
92 return (fbc->counters != NULL);
93 }
94
95 #else /* !CONFIG_SMP */
96
97 struct percpu_counter {
98 s64 count;
99 };
100
percpu_counter_init(struct percpu_counter * fbc,s64 amount,gfp_t gfp)101 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
102 gfp_t gfp)
103 {
104 fbc->count = amount;
105 return 0;
106 }
107
percpu_counter_destroy(struct percpu_counter * fbc)108 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
109 {
110 }
111
percpu_counter_set(struct percpu_counter * fbc,s64 amount)112 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
113 {
114 fbc->count = amount;
115 }
116
percpu_counter_compare(struct percpu_counter * fbc,s64 rhs)117 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
118 {
119 if (fbc->count > rhs)
120 return 1;
121 else if (fbc->count < rhs)
122 return -1;
123 else
124 return 0;
125 }
126
127 static inline int
__percpu_counter_compare(struct percpu_counter * fbc,s64 rhs,s32 batch)128 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
129 {
130 return percpu_counter_compare(fbc, rhs);
131 }
132
133 static inline void
percpu_counter_add(struct percpu_counter * fbc,s64 amount)134 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
135 {
136 preempt_disable();
137 fbc->count += amount;
138 preempt_enable();
139 }
140
141 static inline void
percpu_counter_add_batch(struct percpu_counter * fbc,s64 amount,s32 batch)142 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
143 {
144 percpu_counter_add(fbc, amount);
145 }
146
percpu_counter_read(struct percpu_counter * fbc)147 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
148 {
149 return fbc->count;
150 }
151
152 /*
153 * percpu_counter is intended to track positive numbers. In the UP case the
154 * number should never be negative.
155 */
percpu_counter_read_positive(struct percpu_counter * fbc)156 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
157 {
158 return fbc->count;
159 }
160
percpu_counter_sum_positive(struct percpu_counter * fbc)161 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
162 {
163 return percpu_counter_read_positive(fbc);
164 }
165
percpu_counter_sum(struct percpu_counter * fbc)166 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
167 {
168 return percpu_counter_read(fbc);
169 }
170
percpu_counter_initialized(struct percpu_counter * fbc)171 static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
172 {
173 return true;
174 }
175
percpu_counter_sync(struct percpu_counter * fbc)176 static inline void percpu_counter_sync(struct percpu_counter *fbc)
177 {
178 }
179 #endif /* CONFIG_SMP */
180
percpu_counter_inc(struct percpu_counter * fbc)181 static inline void percpu_counter_inc(struct percpu_counter *fbc)
182 {
183 percpu_counter_add(fbc, 1);
184 }
185
percpu_counter_dec(struct percpu_counter * fbc)186 static inline void percpu_counter_dec(struct percpu_counter *fbc)
187 {
188 percpu_counter_add(fbc, -1);
189 }
190
percpu_counter_sub(struct percpu_counter * fbc,s64 amount)191 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
192 {
193 percpu_counter_add(fbc, -amount);
194 }
195
196 #endif /* _LINUX_PERCPU_COUNTER_H */
197