v4.19.13 snapshot.
diff --git a/lib/ratelimit.c b/lib/ratelimit.c
new file mode 100644
index 0000000..d01f471
--- /dev/null
+++ b/lib/ratelimit.c
@@ -0,0 +1,71 @@
+/*
+ * ratelimit.c - Do something with rate limit.
+ *
+ * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
+ *
+ * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
+ * parameter. Now every user can use their own standalone ratelimit_state.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/ratelimit.h>
+#include <linux/jiffies.h>
+#include <linux/export.h>
+
+/*
+ * __ratelimit - rate limiting
+ * @rs: ratelimit_state data
+ * @func: name of calling function
+ *
+ * This enforces a rate limit: not more than @rs->burst callbacks
+ * in every @rs->interval
+ *
+ * RETURNS:
+ * 0 means callbacks will be suppressed.
+ * 1 means go ahead and do it.
+ */
+int ___ratelimit(struct ratelimit_state *rs, const char *func)
+{
+ unsigned long flags;
+ int ret;
+
+ if (!rs->interval)
+ return 1;
+
+ /*
+ * If we contend on this state's lock then almost
+ * by definition we are too busy to print a message,
+ * in addition to the one that will be printed by
+ * the entity that is holding the lock already:
+ */
+ if (!raw_spin_trylock_irqsave(&rs->lock, flags))
+ return 0;
+
+ if (!rs->begin)
+ rs->begin = jiffies;
+
+ if (time_is_before_jiffies(rs->begin + rs->interval)) {
+ if (rs->missed) {
+ if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
+ printk_deferred(KERN_WARNING
+ "%s: %d callbacks suppressed\n",
+ func, rs->missed);
+ rs->missed = 0;
+ }
+ }
+ rs->begin = jiffies;
+ rs->printed = 0;
+ }
+ if (rs->burst && rs->burst > rs->printed) {
+ rs->printed++;
+ ret = 1;
+ } else {
+ rs->missed++;
+ ret = 0;
+ }
+ raw_spin_unlock_irqrestore(&rs->lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL(___ratelimit);