linux-kernel - [PATCH 3.16.y-ckt 179/180] cifs: Ratelimit kernel log messages

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Message-Id: <1454538786-12215-180-git-send-email-luis.henriques@canonical.com>
Date:	Wed,  3 Feb 2016 22:33:05 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jamie Bainbridge <jamie.bainbridge@...il.com>,
	Steve French <smfrench@...il.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 179/180] cifs: Ratelimit kernel log messages

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 fs/cifs/cifs_debug.c |  2 +-
 fs/cifs/cifs_debug.h | 10 ++++------
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index f3ac4154cbb6..a7e223bbf8df 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -68,7 +68,7 @@ void cifs_vfs_err(const char *fmt, ...)
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	printk(KERN_ERR "CIFS VFS: %pV", &vaf);
+	pr_err_ratelimited("CIFS VFS: %pV", &vaf);
 
 	va_end(args);
 }
diff --git a/fs/cifs/cifs_debug.h b/fs/cifs/cifs_debug.h
index c99b40fb609b..9ebeb6f19c8a 100644
--- a/fs/cifs/cifs_debug.h
+++ b/fs/cifs/cifs_debug.h
@@ -51,15 +51,13 @@ __printf(1, 2) void cifs_vfs_err(const char *fmt, ...);
 /* information message: e.g., configuration, major event */
 #define cifs_dbg(type, fmt, ...)					\
 do {									\
-	if (type == FYI) {						\
-		if (cifsFYI & CIFS_INFO) {				\
-			printk(KERN_DEBUG "%s: " fmt,			\
-			       __FILE__, ##__VA_ARGS__);		\
-		}							\
+	if (type == FYI && cifsFYI & CIFS_INFO) {			\
+		pr_debug_ratelimited("%s: "				\
+			    fmt, __FILE__, ##__VA_ARGS__);		\
 	} else if (type == VFS) {					\
 		cifs_vfs_err(fmt, ##__VA_ARGS__);			\
 	} else if (type == NOISY && type != 0) {			\
-		printk(KERN_DEBUG fmt, ##__VA_ARGS__);			\
+		pr_debug_ratelimited(fmt, ##__VA_ARGS__);		\
 	}								\
 } while (0)