dm vdo: use a short static string for thread name prefix

Also remove MODULE_NAME and a BUG_ON check, both unneeded.

This fixes a warning about string truncation in snprintf that
will never happen in practice:

drivers/md/dm-vdo/vdo.c: In function ‘vdo_make’:
drivers/md/dm-vdo/vdo.c:564:5: error: ‘%s’ directive output may be truncated writing up to 55 bytes into a region of size 16 [-Werror=format-truncation=]
    "%s%u", MODULE_NAME, instance);
     ^~
drivers/md/dm-vdo/vdo.c:563:2: note: ‘snprintf’ output between 2 and 66 bytes into a destination of size 16
  snprintf(vdo->thread_name_prefix, sizeof(vdo->thread_name_prefix),
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    "%s%u", MODULE_NAME, instance);
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reported-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Matthew Sakai <msakai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Author: lorelei-sakai

drivers/md/dm-vdo/vdo.c

@@ -31,9 +31,7 @@
 
 #include <linux/completion.h>
 #include <linux/device-mapper.h>
-#include <linux/kernel.h>
 #include <linux/lz4.h>
-#include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
@@ -142,12 +140,6 @@ static void finish_vdo_request_queue(void *ptr)
 	vdo_unregister_allocating_thread();
 }
 
-#ifdef MODULE
-#define MODULE_NAME THIS_MODULE->name
-#else
-#define MODULE_NAME "dm-vdo"
-#endif  /* MODULE */
-
 static const struct vdo_work_queue_type default_queue_type = {
 	.start = start_vdo_request_queue,
 	.finish = finish_vdo_request_queue,
@@ -559,8 +551,7 @@ int vdo_make(unsigned int instance, struct device_config *config, char **reason,
 	*vdo_ptr = vdo;
 
 	snprintf(vdo->thread_name_prefix, sizeof(vdo->thread_name_prefix),
-		 "%s%u", MODULE_NAME, instance);
-	BUG_ON(vdo->thread_name_prefix[0] == '\0');
+		 "vdo%u", instance);
 	result = vdo_allocate(vdo->thread_config.thread_count,
 			      struct vdo_thread, __func__, &vdo->threads);
 	if (result != VDO_SUCCESS) {