scst_vdisk: Rate-limit block I/O error messages

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6810 d57e44dd-8a1f-0410-8b47-8ef2f437770f

scst/include/backport.h

@@ -365,6 +365,28 @@ static inline __attribute__ ((format (printf, 1, 2)))
 int no_printk(const char *s, ...) { return 0; }
 #endif
 
+/* <linux/ratelimit.h> */
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 27)
+/* See also commit 717115e1a585 */
+
+#define DEFAULT_RATELIMIT_INTERVAL (5 * HZ)
+#define DEFAULT_RATELIMIT_BURST 10
+
+struct ratelimit_state {
+	int interval;
+	int burst;
+};
+
+#define DEFINE_RATELIMIT_STATE(name, interval, burst)	\
+	struct ratelimit_state name = {interval, burst,}
+
+static inline int __ratelimit(struct ratelimit_state *rs)
+{
+	return 1;
+}
+#endif
+
 /* <linux/rcupdate.h> */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 0, 0) && !defined(kfree_rcu)

scst/include/scst_debug.h

@@ -31,6 +31,10 @@
 #include <linux/bug.h>		/* for WARN_ON_ONCE */
 #endif
 
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 27)
+#include <linux/ratelimit.h>
+#endif
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 28)
 /*
  * See also the following commits:
@@ -284,6 +288,16 @@ do {									\
 
 #endif /* CONFIG_SCST_DEBUG || CONFIG_SCST_TRACING */
 
+#define PRINT_ERROR_RATELIMITED(format, args...)	\
+	do {						\
+		static DEFINE_RATELIMIT_STATE(_rs,      \
+			DEFAULT_RATELIMIT_INTERVAL,	\
+			DEFAULT_RATELIMIT_BURST);	\
+							\
+		if (__ratelimit(&_rs))			\
+			PRINT_ERROR(format, ##args);	\
+	} while (0)
+
 #ifdef CONFIG_SCST_DEBUG
 
 #define TRACE_DBG_FLAG(trace, format, args...)				\

scst/src/dev_handlers/scst_vdisk.c

@@ -6486,7 +6486,8 @@ static void blockio_endio(struct bio *bio)
 	if (unlikely(error != 0)) {
 		unsigned long flags;
 
-		PRINT_ERROR("BLOCKIO for cmd %p finished with error %d",
+		PRINT_ERROR_RATELIMITED(
+			"BLOCKIO for cmd %p finished with error %d",
 			blockio_work->cmd, error);
 
 		/*