dynamic_debug: refactor dynamic_pr_debug and friends

For the upcoming 'define the _ddebug descriptor in assembly', we need
all the descriptors in a translation unit to have distinct names
(because asm does not understand C scope).  The easiest way to achieve
that is as usual with an extra level of macros, passing the identifier
to use to the innermost macro, generating it via __UNIQUE_ID or
something.

However, instead of repeating that exercise for dynamic_pr_debug,
dynamic_dev_dbg, dynamic_netdev_dbg and dynamic_hex_dump separately, we
can use the similarity between their bodies to implement them via a
common macro, _dynamic_func_call - though the hex_dump case requires a
slight variant, since print_hex_dump does not take the _ddebug
descriptor.  We'll also get to use that variant elsewhere (btrfs).

Link: http://lkml.kernel.org/r/20190212214150.4807-11-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Jason Baron <jbaron@akamai.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/dynamic_debug.h

@@ -112,40 +112,54 @@ void __dynamic_netdev_dbg(struct _ddebug *descriptor,
 
 #endif
 
-#define dynamic_pr_debug(fmt, ...)				\
-do {								\
-	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);		\
-	if (DYNAMIC_DEBUG_BRANCH(descriptor))			\
-		__dynamic_pr_debug(&descriptor, pr_fmt(fmt),	\
-				   ##__VA_ARGS__);		\
+#define __dynamic_func_call(id, fmt, func, ...) do {	\
+	DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt);		\
+	if (DYNAMIC_DEBUG_BRANCH(id))			\
+		func(&id, ##__VA_ARGS__);		\
 } while (0)
 
+#define __dynamic_func_call_no_desc(id, fmt, func, ...) do {	\
+	DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt);			\
+	if (DYNAMIC_DEBUG_BRANCH(id))				\
+		func(__VA_ARGS__);				\
+} while (0)
+
+/*
+ * "Factory macro" for generating a call to func, guarded by a
+ * DYNAMIC_DEBUG_BRANCH. The dynamic debug decriptor will be
+ * initialized using the fmt argument. The function will be called with
+ * the address of the descriptor as first argument, followed by all
+ * the varargs. Note that fmt is repeated in invocations of this
+ * macro.
+ */
+#define _dynamic_func_call(fmt, func, ...)				\
+	__dynamic_func_call(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)
+/*
+ * A variant that does the same, except that the descriptor is not
+ * passed as the first argument to the function; it is only called
+ * with precisely the macro's varargs.
+ */
+#define _dynamic_func_call_no_desc(fmt, func, ...)	\
+	__dynamic_func_call_no_desc(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)
+
+#define dynamic_pr_debug(fmt, ...)				\
+	_dynamic_func_call(fmt,	__dynamic_pr_debug,		\
+			   pr_fmt(fmt), ##__VA_ARGS__)
+
 #define dynamic_dev_dbg(dev, fmt, ...)				\
-do {								\
-	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);		\
-	if (DYNAMIC_DEBUG_BRANCH(descriptor))			\
-		__dynamic_dev_dbg(&descriptor, dev, fmt,	\
-				  ##__VA_ARGS__);		\
-} while (0)
+	_dynamic_func_call(fmt,__dynamic_dev_dbg, 		\
+			   dev, fmt, ##__VA_ARGS__)
 
 #define dynamic_netdev_dbg(dev, fmt, ...)			\
-do {								\
-	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);		\
-	if (DYNAMIC_DEBUG_BRANCH(descriptor))			\
-		__dynamic_netdev_dbg(&descriptor, dev, fmt,	\
-				     ##__VA_ARGS__);		\
-} while (0)
+	_dynamic_func_call(fmt, __dynamic_netdev_dbg,		\
+			   dev, fmt, ##__VA_ARGS__)
 
-#define dynamic_hex_dump(prefix_str, prefix_type, rowsize,	\
-			 groupsize, buf, len, ascii)		\
-do {								\
-	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor,		\
-		__builtin_constant_p(prefix_str) ? prefix_str : "hexdump");\
-	if (DYNAMIC_DEBUG_BRANCH(descriptor))			\
-		print_hex_dump(KERN_DEBUG, prefix_str,		\
-			       prefix_type, rowsize, groupsize,	\
-			       buf, len, ascii);		\
-} while (0)
+#define dynamic_hex_dump(prefix_str, prefix_type, rowsize,		\
+			 groupsize, buf, len, ascii)			\
+	_dynamic_func_call_no_desc(__builtin_constant_p(prefix_str) ? prefix_str : "hexdump", \
+				   print_hex_dump,			\
+				   KERN_DEBUG, prefix_str, prefix_type,	\
+				   rowsize, groupsize, buf, len, ascii)
 
 #else