UBI: improve checking in debugging prints

When debugging is disabled, define debugging prints as if (0) printk() to make
sure that the compiler still the format string in debugging messages even if
debugging is disabled.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/debug.h

@@ -184,14 +184,31 @@ static inline int ubi_dbg_is_erase_failure(void)
 
 #else
 
-#define ubi_assert(expr)                 ({})
-#define dbg_err(fmt, ...)                ({})
-#define dbg_msg(fmt, ...)                ({})
-#define dbg_gen(fmt, ...)                ({})
-#define dbg_eba(fmt, ...)                ({})
-#define dbg_wl(fmt, ...)                 ({})
-#define dbg_io(fmt, ...)                 ({})
-#define dbg_bld(fmt, ...)                ({})
+/* Use "if (0)" to make compiler check arguments even if debugging is off */
+#define ubi_assert(expr)  do {                                               \
+	if (0) {                                                             \
+		printk(KERN_CRIT "UBI assert failed in %s at %u (pid %d)\n", \
+		       __func__, __LINE__, current->pid);                    \
+	}                                                                    \
+} while (0)
+
+#define dbg_err(fmt, ...) do {                                               \
+	if (0)                                                               \
+		ubi_err(fmt, ##__VA_ARGS__);                                 \
+} while (0)
+
+#define dbg_msg(fmt, ...) do {                                               \
+	if (0)                                                               \
+		printk(KERN_DEBUG "UBI DBG (pid %d): %s: " fmt "\n",         \
+		       current->pid, __func__, ##__VA_ARGS__);               \
+} while (0)
+
+#define dbg_gen(fmt, ...)  dbg_msg(fmt, ##__VA_ARGS__)
+#define dbg_eba(fmt, ...)  dbg_msg(fmt, ##__VA_ARGS__)
+#define dbg_wl(fmt, ...)   dbg_msg(fmt, ##__VA_ARGS__)
+#define dbg_io(fmt, ...)   dbg_msg(fmt, ##__VA_ARGS__)
+#define dbg_bld(fmt, ...)  dbg_msg(fmt, ##__VA_ARGS__)
+
 #define ubi_dbg_dump_stack()             ({})
 #define ubi_dbg_dump_ec_hdr(ec_hdr)      ({})
 #define ubi_dbg_dump_vid_hdr(vid_hdr)    ({})