vsprintf: Factor out %pV handler as va_format()

Move the code from the long pointer() function. We are going to improve
error handling that will make it more complicated.

This patch does not change the existing behavior.

Link: http://lkml.kernel.org/r/20190417115350.20479-6-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8ca29bc..12b71a4 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1520,6 +1520,17 @@ char *escaped_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
 	return buf;
 }
 
+static char *va_format(char *buf, char *end, struct va_format *va_fmt)
+{
+	va_list va;
+
+	va_copy(va, *va_fmt->va);
+	buf += vsnprintf(buf, end > buf ? end - buf : 0, va_fmt->fmt, va);
+	va_end(va);
+
+	return buf;
+}
+
 static noinline_for_stack
 char *uuid_string(char *buf, char *end, const u8 *addr,
 		  struct printf_spec spec, const char *fmt)
@@ -2046,15 +2057,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'U':
 		return uuid_string(buf, end, ptr, spec, fmt);
 	case 'V':
-		{
-			va_list va;
-
-			va_copy(va, *((struct va_format *)ptr)->va);
-			buf += vsnprintf(buf, end > buf ? end - buf : 0,
-					 ((struct va_format *)ptr)->fmt, va);
-			va_end(va);
-			return buf;
-		}
+		return va_format(buf, end, ptr);
 	case 'K':
 		return restricted_pointer(buf, end, ptr, spec);
 	case 'N':