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>

include/linux/kernel.h

@@ -188,6 +188,7 @@ extern int log_buf_copy(char *dest, int idx, int len);
 extern int printk_ratelimit_jiffies;
 extern int printk_ratelimit_burst;
 extern int printk_ratelimit(void);
+extern int __ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 				   unsigned int interval_msec);

kernel/printk.c

@@ -1287,31 +1287,7 @@ void tty_write_message(struct tty_struct *tty, char *msg)
  */
 int __printk_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 "printk: %d messages suppressed.\n", lost);
-		return 1;
-	}
-	missed++;
-	spin_unlock_irqrestore(&ratelimit_lock, flags);
-	return 0;
+	return __ratelimit(ratelimit_jiffies, ratelimit_burst);
 }
 EXPORT_SYMBOL(__printk_ratelimit);
 

lib/Makefile

@@ -6,7 +6,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o \
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
-	 proportions.o prio_heap.o
+	 proportions.o prio_heap.o ratelimit.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o

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);