| 1 | |
| 2 | |
| 3 | * ratelimit.c - Do something with rate limit.
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| 4 | *
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| 5 | * Isolated from kernel/printk.c by Dave Young <[email protected]>
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| 6 | *
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| 7 | * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
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| 8 | * parameter. Now every user can use their own standalone ratelimit_state.
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| 9 |
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| 10 |
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| 11 | #include <linux/ratelimit.h>
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| 12 | #include <linux/jiffies.h>
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| 13 | #include <linux/export.h>
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| 14 |
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| 15 | |
| 16 | * __ratelimit - rate limiting
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| 17 | * @rs: ratelimit_state data
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| 18 | * @func: name of calling function
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| 19 | *
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| 20 | * This enforces a rate limit: not more than @rs->burst callbacks
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| 21 | * in every @rs->interval
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| 22 | *
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| 23 | * RETURNS:
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| 24 | * 0 means callbacks will be suppressed.
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| 25 | * 1 means go ahead and do it.
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| 26 |
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| 27 | int ___ratelimit(struct ratelimit_state *rs, const char *func)
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| 28 | {
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| 29 | |
| 30 | * Changing two values separately could be inconsistent
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| 31 | * and some message could be lost. (See: net_ratelimit_state).
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| 32 |
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| 33 | int interval = READ_ONCE(rs->interval);
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| 34 | int burst = READ_ONCE(rs->burst);
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| 35 | unsigned long flags;
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| 36 | int ret = 0;
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| 37 |
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| 38 | |
| 39 | * Zero interval says never limit, otherwise, non-positive burst
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| 40 | * says always limit.
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| 41 |
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| 42 | if (interval <= 0 || burst <= 0) {
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| 43 | WARN_ONCE(interval < 0 || burst < 0, "Negative interval (%d) or burst (%d): Uninitialized ratelimit_state structure?\n", interval, burst);
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| 44 | ret = interval == 0 || burst > 0;
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| 45 | if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) || (!interval && !burst) ||
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| 46 | !raw_spin_trylock_irqsave(&rs->lock, flags))
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| 47 | goto nolock_ret;
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| 48 |
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| 49 |
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| 50 | rs->flags &= ~RATELIMIT_INITIALIZED;
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| 51 | goto unlock_ret;
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| 52 | }
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| 53 |
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| 54 | |
| 55 | * If we contend on this state's lock then just check if
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| 56 | * the current burst is used or not. It might cause
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| 57 | * false positive when we are past the interval and
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| 58 | * the current lock owner is just about to reset it.
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| 59 |
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| 60 | if (!raw_spin_trylock_irqsave(&rs->lock, flags)) {
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| 61 | if (READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED &&
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| 62 | atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
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| 63 | ret = 1;
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| 64 | goto nolock_ret;
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| 65 | }
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| 66 |
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| 67 | if (!(rs->flags & RATELIMIT_INITIALIZED)) {
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| 68 | rs->begin = jiffies;
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| 69 | rs->flags |= RATELIMIT_INITIALIZED;
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| 70 | atomic_set(&rs->rs_n_left, rs->burst);
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| 71 | }
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| 72 |
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| 73 | if (time_is_before_jiffies(rs->begin + interval)) {
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| 74 | int m;
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| 75 |
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| 76 | |
| 77 | * Reset rs_n_left ASAP to reduce false positives
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| 78 | * in parallel calls, see above.
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| 79 |
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| 80 | atomic_set(&rs->rs_n_left, rs->burst);
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| 81 | rs->begin = jiffies;
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| 82 |
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| 83 | if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
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| 84 | m = ratelimit_state_reset_miss(rs);
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| 85 | if (m) {
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| 86 | printk_deferred(KERN_WARNING
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| 87 | "%s: %d callbacks suppressed\n", func, m);
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| 88 | }
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| 89 | }
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| 90 | }
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| 91 |
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| 92 |
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| 93 | if (atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
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| 94 | ret = 1;
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| 95 |
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| 96 | unlock_ret:
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| 97 | raw_spin_unlock_irqrestore(&rs->lock, flags);
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| 98 |
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| 99 | nolock_ret:
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| 100 | if (!ret)
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| 101 | ratelimit_state_inc_miss(rs);
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| 102 |
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| 103 | return ret;
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| 104 | }
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| 105 | EXPORT_SYMBOL(___ratelimit);
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