isolate ratelimit from printk.c for other use

Due to the rcupreempt.h WARN_ON trigged, I got 2G syslog file.  For some
serious complaining of kernel, we need repeat the warnings, so here I isolate
the ratelimit part of printk.c to a standalone file.

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
new file mode 100644
index 000000000000..485e3040dcd4
--- /dev/null
+++ b/lib/ratelimit.c
@@ -0,0 +1,51 @@
+/*
+ * ratelimit.c - Do something with rate limit.
+ *
+ * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
+ *
+ * This file is released under the GPLv2.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+
+/*
+ * __ratelimit - rate limiting
+ * @ratelimit_jiffies: minimum time in jiffies between two callbacks
+ * @ratelimit_burst: number of callbacks we do before ratelimiting
+ *
+ * This enforces a rate limit: not more than @ratelimit_burst callbacks
+ * in every ratelimit_jiffies
+ */
+int __ratelimit(int ratelimit_jiffies, int ratelimit_burst)
+{
+        static DEFINE_SPINLOCK(ratelimit_lock);
+        static unsigned toks = 10 * 5 * HZ;
+        static unsigned long last_msg;
+        static int missed;
+        unsigned long flags;
+        unsigned long now = jiffies;
+
+        spin_lock_irqsave(&ratelimit_lock, flags);
+        toks += now - last_msg;
+        last_msg = now;
+        if (toks > (ratelimit_burst * ratelimit_jiffies))
+                toks = ratelimit_burst * ratelimit_jiffies;
+        if (toks >= ratelimit_jiffies) {
+                int lost = missed;
+
+                missed = 0;
+                toks -= ratelimit_jiffies;
+                spin_unlock_irqrestore(&ratelimit_lock, flags);
+                if (lost)
+                        printk(KERN_WARNING "%s: %d messages suppressed\n",
+                                __func__, lost);
+                return 1;
+        }
+        missed++;
+        spin_unlock_irqrestore(&ratelimit_lock, flags);
+        return 0;
+}
+EXPORT_SYMBOL(__ratelimit);