Rev 422 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 422 | giacomo | 1 | /* |
| 2 | * A simple "approximate counter" for use in ext2 and ext3 superblocks. |
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| 3 | * |
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| 4 | * WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4. |
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| 5 | */ |
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| 6 | |||
| 7 | #include <linux/config.h> |
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| 8 | #include <linux/spinlock.h> |
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| 9 | #include <linux/smp.h> |
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| 10 | #include <linux/threads.h> |
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| 11 | |||
| 12 | #ifdef CONFIG_SMP |
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| 13 | |||
| 14 | struct __percpu_counter { |
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| 15 | long count; |
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| 16 | } ____cacheline_aligned; |
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| 17 | |||
| 18 | struct percpu_counter { |
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| 19 | spinlock_t lock; |
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| 20 | long count; |
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| 21 | struct __percpu_counter counters[NR_CPUS]; |
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| 22 | }; |
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| 23 | |||
| 24 | #if NR_CPUS >= 16 |
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| 25 | #define FBC_BATCH (NR_CPUS*2) |
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| 26 | #else |
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| 27 | #define FBC_BATCH (NR_CPUS*4) |
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| 28 | #endif |
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| 29 | |||
| 30 | static inline void percpu_counter_init(struct percpu_counter *fbc) |
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| 31 | { |
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| 32 | int i; |
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| 33 | |||
| 34 | spin_lock_init(&fbc->lock); |
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| 35 | fbc->count = 0; |
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| 36 | for (i = 0; i < NR_CPUS; i++) |
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| 37 | fbc->counters[i].count = 0; |
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| 38 | } |
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| 39 | |||
| 40 | void percpu_counter_mod(struct percpu_counter *fbc, long amount); |
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| 41 | |||
| 42 | static inline long percpu_counter_read(struct percpu_counter *fbc) |
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| 43 | { |
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| 44 | return fbc->count; |
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| 45 | } |
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| 46 | |||
| 47 | /* |
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| 48 | * It is possible for the percpu_counter_read() to return a small negative |
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| 49 | * number for some counter which should never be negative. |
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| 50 | */ |
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| 51 | static inline long percpu_counter_read_positive(struct percpu_counter *fbc) |
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| 52 | { |
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| 53 | long ret = fbc->count; |
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| 54 | |||
| 55 | barrier(); /* Prevent reloads of fbc->count */ |
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| 56 | if (ret > 0) |
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| 57 | return ret; |
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| 58 | return 1; |
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| 59 | } |
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| 60 | |||
| 61 | #else |
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| 62 | |||
| 63 | struct percpu_counter { |
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| 64 | long count; |
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| 65 | }; |
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| 66 | |||
| 67 | static inline void percpu_counter_init(struct percpu_counter *fbc) |
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| 68 | { |
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| 69 | fbc->count = 0; |
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| 70 | } |
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| 71 | |||
| 72 | static inline void |
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| 73 | percpu_counter_mod(struct percpu_counter *fbc, long amount) |
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| 74 | { |
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| 75 | preempt_disable(); |
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| 76 | fbc->count += amount; |
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| 77 | preempt_enable(); |
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| 78 | } |
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| 79 | |||
| 80 | static inline long percpu_counter_read(struct percpu_counter *fbc) |
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| 81 | { |
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| 82 | return fbc->count; |
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| 83 | } |
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| 84 | |||
| 85 | static inline long percpu_counter_read_positive(struct percpu_counter *fbc) |
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| 86 | { |
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| 87 | return fbc->count; |
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| 88 | } |
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| 89 | |||
| 90 | #endif /* CONFIG_SMP */ |
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| 91 | |||
| 92 | static inline void percpu_counter_inc(struct percpu_counter *fbc) |
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| 93 | { |
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| 94 | percpu_counter_mod(fbc, 1); |
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| 95 | } |
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| 96 | |||
| 97 | static inline void percpu_counter_dec(struct percpu_counter *fbc) |
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| 98 | { |
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| 99 | percpu_counter_mod(fbc, -1); |
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| 100 | } |