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 17 /* percpu_counter batch for local add or sub */ 18 #define PERCPU_COUNTER_LOCAL_BATCH INT_MAX 19 20 #ifdef CONFIG_SMP 21 22 struct percpu_counter { 23 raw_spinlock_t lock; 24 s64 count; 25 #ifdef CONFIG_HOTPLUG_CPU 26 struct list_head list; /* All percpu_counters are on a list */ 27 #endif 28 s32 __percpu *counters; 29 }; 30 31 extern int percpu_counter_batch; 32 33 int __percpu_counter_init_many(struct percpu_counter *fbc, s64 amount, 34 gfp_t gfp, u32 nr_counters, 35 struct lock_class_key *key); 36 37 #define percpu_counter_init_many(fbc, value, gfp, nr_counters) \ 38 ({ \ 39 static struct lock_class_key __key; \ 40 \ 41 __percpu_counter_init_many(fbc, value, gfp, nr_counters,\ 42 &__key); \ 43 }) 44 45 46 #define percpu_counter_init(fbc, value, gfp) \ 47 percpu_counter_init_many(fbc, value, gfp, 1) 48 49 void percpu_counter_destroy_many(struct percpu_counter *fbc, u32 nr_counters); 50 static inline void percpu_counter_destroy(struct percpu_counter *fbc) 51 { 52 percpu_counter_destroy_many(fbc, 1); 53 } 54 55 void percpu_counter_set(struct percpu_counter *fbc, s64 amount); 56 void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, 57 s32 batch); 58 s64 __percpu_counter_sum(struct percpu_counter *fbc); 59 int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch); 60 void percpu_counter_sync(struct percpu_counter *fbc); 61 62 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) 63 { 64 return __percpu_counter_compare(fbc, rhs, percpu_counter_batch); 65 } 66 67 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount) 68 { 69 percpu_counter_add_batch(fbc, amount, percpu_counter_batch); 70 } 71 72 /* 73 * With percpu_counter_add_local() and percpu_counter_sub_local(), counts 74 * are accumulated in local per cpu counter and not in fbc->count until 75 * local count overflows PERCPU_COUNTER_LOCAL_BATCH. This makes counter 76 * write efficient. 77 * But percpu_counter_sum(), instead of percpu_counter_read(), needs to be 78 * used to add up the counts from each CPU to account for all the local 79 * counts. So percpu_counter_add_local() and percpu_counter_sub_local() 80 * should be used when a counter is updated frequently and read rarely. 81 */ 82 static inline void 83 percpu_counter_add_local(struct percpu_counter *fbc, s64 amount) 84 { 85 percpu_counter_add_batch(fbc, amount, PERCPU_COUNTER_LOCAL_BATCH); 86 } 87 88 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc) 89 { 90 s64 ret = __percpu_counter_sum(fbc); 91 return ret < 0 ? 0 : ret; 92 } 93 94 static inline s64 percpu_counter_sum(struct percpu_counter *fbc) 95 { 96 return __percpu_counter_sum(fbc); 97 } 98 99 static inline s64 percpu_counter_read(struct percpu_counter *fbc) 100 { 101 return fbc->count; 102 } 103 104 /* 105 * It is possible for the percpu_counter_read() to return a small negative 106 * number for some counter which should never be negative. 107 * 108 */ 109 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) 110 { 111 /* Prevent reloads of fbc->count */ 112 s64 ret = READ_ONCE(fbc->count); 113 114 if (ret >= 0) 115 return ret; 116 return 0; 117 } 118 119 static inline bool percpu_counter_initialized(struct percpu_counter *fbc) 120 { 121 return (fbc->counters != NULL); 122 } 123 124 #else /* !CONFIG_SMP */ 125 126 struct percpu_counter { 127 s64 count; 128 }; 129 130 static inline int percpu_counter_init_many(struct percpu_counter *fbc, 131 s64 amount, gfp_t gfp, 132 u32 nr_counters) 133 { 134 u32 i; 135 136 for (i = 0; i < nr_counters; i++) 137 fbc[i].count = amount; 138 139 return 0; 140 } 141 142 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount, 143 gfp_t gfp) 144 { 145 return percpu_counter_init_many(fbc, amount, gfp, 1); 146 } 147 148 static inline void percpu_counter_destroy_many(struct percpu_counter *fbc, 149 u32 nr_counters) 150 { 151 } 152 153 static inline void percpu_counter_destroy(struct percpu_counter *fbc) 154 { 155 } 156 157 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount) 158 { 159 fbc->count = amount; 160 } 161 162 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) 163 { 164 if (fbc->count > rhs) 165 return 1; 166 else if (fbc->count < rhs) 167 return -1; 168 else 169 return 0; 170 } 171 172 static inline int 173 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch) 174 { 175 return percpu_counter_compare(fbc, rhs); 176 } 177 178 static inline void 179 percpu_counter_add(struct percpu_counter *fbc, s64 amount) 180 { 181 unsigned long flags; 182 183 local_irq_save(flags); 184 fbc->count += amount; 185 local_irq_restore(flags); 186 } 187 188 /* non-SMP percpu_counter_add_local is the same with percpu_counter_add */ 189 static inline void 190 percpu_counter_add_local(struct percpu_counter *fbc, s64 amount) 191 { 192 percpu_counter_add(fbc, amount); 193 } 194 195 static inline void 196 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch) 197 { 198 percpu_counter_add(fbc, amount); 199 } 200 201 static inline s64 percpu_counter_read(struct percpu_counter *fbc) 202 { 203 return fbc->count; 204 } 205 206 /* 207 * percpu_counter is intended to track positive numbers. In the UP case the 208 * number should never be negative. 209 */ 210 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) 211 { 212 return fbc->count; 213 } 214 215 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc) 216 { 217 return percpu_counter_read_positive(fbc); 218 } 219 220 static inline s64 percpu_counter_sum(struct percpu_counter *fbc) 221 { 222 return percpu_counter_read(fbc); 223 } 224 225 static inline bool percpu_counter_initialized(struct percpu_counter *fbc) 226 { 227 return true; 228 } 229 230 static inline void percpu_counter_sync(struct percpu_counter *fbc) 231 { 232 } 233 #endif /* CONFIG_SMP */ 234 235 static inline void percpu_counter_inc(struct percpu_counter *fbc) 236 { 237 percpu_counter_add(fbc, 1); 238 } 239 240 static inline void percpu_counter_dec(struct percpu_counter *fbc) 241 { 242 percpu_counter_add(fbc, -1); 243 } 244 245 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount) 246 { 247 percpu_counter_add(fbc, -amount); 248 } 249 250 static inline void 251 percpu_counter_sub_local(struct percpu_counter *fbc, s64 amount) 252 { 253 percpu_counter_add_local(fbc, -amount); 254 } 255 256 #endif /* _LINUX_PERCPU_COUNTER_H */ 257