linux-kernel - [PATCH 3.2 50/87] cifs: Ratelimit kernel log messages

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Message-ID: <lsq.1454975631.940388372@decadent.org.uk>
Date:	Mon, 08 Feb 2016 23:53:51 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Jamie Bainbridge" <jamie.bainbridge@...il.com>,
	"Steve French" <smfrench@...il.com>
Subject: [PATCH 3.2 50/87] cifs: Ratelimit kernel log messages

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

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

From: Jamie Bainbridge <jamie.bainbridge@...il.com>

commit ec7147a99e33a9e4abad6fc6e1b40d15df045d53 upstream.

Under some conditions, CIFS can repeatedly call the cifs_dbg() logging
wrapper. If done rapidly enough, the console framebuffer can softlockup
or "rcu_sched self-detected stall". Apply the built-in log ratelimiters
to prevent such hangs.

Signed-off-by: Jamie Bainbridge <jamie.bainbridge@...il.com>
Signed-off-by: Steve French <smfrench@...il.com>
[bwh: Backported to 3.2:
 - cifs_dbg() and cifs_vfs_err() do not exist, but make similar changes
   to cifsfyi(), cifswarn() and cifserror()]
 - Include <linux/ratelimit.h> explicitly]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/cifs_debug.c | 2 +-
 fs/cifs/cifs_debug.h | 9 ++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

--- a/fs/cifs/cifs_debug.h
+++ b/fs/cifs/cifs_debug.h
@@ -23,6 +23,8 @@
 #ifndef _H_CIFS_DEBUG
 #define _H_CIFS_DEBUG
 
+#include <linux/ratelimit.h>
+
 void cifs_dump_mem(char *label, void *data, int length);
 #ifdef CONFIG_CIFS_DEBUG2
 #define DBG2 2
@@ -48,7 +50,7 @@ extern int cifsFYI;
 #define cifsfyi(fmt, arg...)						\
 do {									\
 	if (cifsFYI & CIFS_INFO)					\
-		printk(KERN_DEBUG "%s: " fmt "\n", __FILE__, ##arg);	\
+		pr_debug_ratelimited("%s: " fmt "\n", __FILE__, ##arg); \
 } while (0)
 
 #define cFYI(set, fmt, arg...)			\
@@ -58,7 +60,7 @@ do {						\
 } while (0)
 
 #define cifswarn(fmt, arg...)			\
-	printk(KERN_WARNING fmt "\n", ##arg)
+	pr_warn_ratelimited(fmt "\n", ##arg)
 
 /* debug event message: */
 extern int cifsERROR;
@@ -73,7 +75,7 @@ do {									\
 #define cifserror(fmt, arg...)					\
 do {								\
 	if (cifsERROR)						\
-		printk(KERN_ERR "CIFS VFS: " fmt "\n", ##arg);	\
+		pr_err_ratelimited("CIFS VFS: " fmt "\n", ##arg);	\
 } while (0)
 
 #define cERROR(set, fmt, arg...)		\