dynamic_debug: move pr_err from module.c to ddebug_add_module

This serves two purposes: First, we get a diagnostic if (though
extremely unlikely), any of the calls of ddebug_add_module for built-in
code fails, effectively disabling dynamic_debug.  Second, I want to make
struct _ddebug opaque, and avoid accessing any of its members outside
dynamic_debug.[ch].

Link: http://lkml.kernel.org/r/20190212214150.4807-9-linux@rasmusvillemoes.dkSigned-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>

kernel/module.c

@@ -2720,9 +2720,7 @@ static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsig
 	if (!debug)
 		return;
 #ifdef CONFIG_DYNAMIC_DEBUG
-	if (ddebug_add_module(debug, num, mod->name))
-		pr_err("dynamic debug error adding module: %s\n",
-			debug->modname);
+	ddebug_add_module(debug, num, mod->name);
 #endif
 }
 

lib/dynamic_debug.c

@@ -849,8 +849,10 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n,
 	struct ddebug_table *dt;
 
 	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
-	if (dt == NULL)
+	if (dt == NULL) {
+		pr_err("error adding module: %s\n", name);
 		return -ENOMEM;
+	}
 	/*
 	 * For built-in modules, name lives in .rodata and is
 	 * immortal. For loaded modules, name points at the name[]