[PATCH] cifs: Ratelimit kernel log messages

From: Jamie Bainbridge <jamie.bainbridge-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [PATCH] cifs: Ratelimit kernel log messages
Date: Sat,  7 Nov 2015 22:13:49 +1000	[thread overview]
Message-ID: <7094bd3a2ef3c030463aa04fbce8369bfb33be9c.1446897962.git.jamie.bainbridge@gmail.com> (raw)

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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 fs/cifs/cifs_debug.c | 2 +-
 fs/cifs/cifs_debug.h | 9 ++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 7febcf2475c5ab675c04dfd2fddaa3ed574522a0..50b268483302922ee63d205a2fa560ec27676eed 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -50,7 +50,7 @@ void cifs_vfs_err(const char *fmt, ...)
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	pr_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 f40fbaca1b2a2c1d7457d71bd1a5e7dd4b477859..66cf0f9fff8984cb12eed1c89d91bc9c6ccc6a9d 100644
--- a/fs/cifs/cifs_debug.h
+++ b/fs/cifs/cifs_debug.h
@@ -51,14 +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) {				\
-			pr_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) {			\
-		pr_debug(fmt, ##__VA_ARGS__);				\
+		pr_debug_ratelimited(fmt, ##__VA_ARGS__);		\
 	}								\
 } while (0)
 
-- 
1.9.1
