linux-kernel - [PATCH 3.16 154/294] dm: fix printk() rate limiting code

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Message-ID: <lsq.1510009382.920073885@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Bart Van Assche" <bart.vanassche@....com>,
        "Mike Snitzer" <snitzer@...hat.com>
Subject: [PATCH 3.16 154/294] dm: fix printk() rate limiting code

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@....com>

commit 604407890ecf624c2fb41013c82b22aade59b455 upstream.

Using the same rate limiting state for different kinds of messages
is wrong because this can cause a high frequency message to suppress
a report of a low frequency message. Hence use a unique rate limiting
state per message type.

Fixes: 71a16736a15e ("dm: use local printk ratelimit")
Signed-off-by: Bart Van Assche <bart.vanassche@....com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/dm.c               | 10 ----------
 include/linux/device-mapper.h | 41 ++++++++++++-----------------------------
 2 files changed, 12 insertions(+), 39 deletions(-)

--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -24,16 +24,6 @@
 
 #define DM_MSG_PREFIX "core"
 
-#ifdef CONFIG_PRINTK
-/*
- * ratelimit state to be used in DMXXX_LIMIT().
- */
-DEFINE_RATELIMIT_STATE(dm_ratelimit_state,
-		       DEFAULT_RATELIMIT_INTERVAL,
-		       DEFAULT_RATELIMIT_BURST);
-EXPORT_SYMBOL(dm_ratelimit_state);
-#endif
-
 /*
  * Cookies are numeric values sent with CHANGE and REMOVE
  * uevents while resuming, removing or renaming the device.
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -481,46 +481,29 @@ void *dm_vcalloc(unsigned long nmemb, un
  *---------------------------------------------------------------*/
 #define DM_NAME "device-mapper"
 
-#ifdef CONFIG_PRINTK
-extern struct ratelimit_state dm_ratelimit_state;
-
-#define dm_ratelimit()	__ratelimit(&dm_ratelimit_state)
-#else
-#define dm_ratelimit()	0
-#endif
+#define DM_RATELIMIT(pr_func, fmt, ...)					\
+do {									\
+	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,	\
+				      DEFAULT_RATELIMIT_BURST);		\
+									\
+	if (__ratelimit(&rs))						\
+		pr_func(DM_FMT(fmt), ##__VA_ARGS__);			\
+} while (0)
 
 #define DM_FMT(fmt) DM_NAME ": " DM_MSG_PREFIX ": " fmt "\n"
 
 #define DMCRIT(fmt, ...) pr_crit(DM_FMT(fmt), ##__VA_ARGS__)
 
 #define DMERR(fmt, ...) pr_err(DM_FMT(fmt), ##__VA_ARGS__)
-#define DMERR_LIMIT(fmt, ...)						\
-do {									\
-	if (dm_ratelimit())						\
-		DMERR(fmt, ##__VA_ARGS__);				\
-} while (0)
-
+#define DMERR_LIMIT(fmt, ...) DM_RATELIMIT(pr_err, fmt, ##__VA_ARGS__)
 #define DMWARN(fmt, ...) pr_warn(DM_FMT(fmt), ##__VA_ARGS__)
-#define DMWARN_LIMIT(fmt, ...)						\
-do {									\
-	if (dm_ratelimit())						\
-		DMWARN(fmt, ##__VA_ARGS__);				\
-} while (0)
-
+#define DMWARN_LIMIT(fmt, ...) DM_RATELIMIT(pr_warn, fmt, ##__VA_ARGS__)
 #define DMINFO(fmt, ...) pr_info(DM_FMT(fmt), ##__VA_ARGS__)
-#define DMINFO_LIMIT(fmt, ...)						\
-do {									\
-	if (dm_ratelimit())						\
-		DMINFO(fmt, ##__VA_ARGS__);				\
-} while (0)
+#define DMINFO_LIMIT(fmt, ...) DM_RATELIMIT(pr_info, fmt, ##__VA_ARGS__)
 
 #ifdef CONFIG_DM_DEBUG
 #define DMDEBUG(fmt, ...) printk(KERN_DEBUG DM_FMT(fmt), ##__VA_ARGS__)
-#define DMDEBUG_LIMIT(fmt, ...)						\
-do {									\
-	if (dm_ratelimit())						\
-		DMDEBUG(fmt, ##__VA_ARGS__);				\
-} while (0)
+#define DMDEBUG_LIMIT(fmt, ...) DM_RATELIMIT(pr_debug, fmt, ##__VA_ARGS__)
 #else
 #define DMDEBUG(fmt, ...) no_printk(fmt, ##__VA_ARGS__)
 #define DMDEBUG_LIMIT(fmt, ...) no_printk(fmt, ##__VA_ARGS__)