jbd2: convert instrumentation from markers to tracepoints

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

include/linux/jbd2.h

@@ -1315,6 +1315,12 @@ extern int jbd_blocks_per_page(struct inode *inode);
 #define BUFFER_TRACE2(bh, bh2, info)	do {} while (0)
 #define JBUFFER_TRACE(jh, info)	do {} while (0)
 
+/* 
+ * jbd2_dev_to_name is a utility function used by the jbd2 and ext4 
+ * tracing infrastructure to map a dev_t to a device name.
+ */
+extern const char *jbd2_dev_to_name(dev_t device);
+
 #endif	/* __KERNEL__ */
 
 #endif	/* _LINUX_JBD2_H */