snprintf is never going to return a negative value, and it will always put a
NULL character at the end of the string. See lib/vsprintf.c::vsnprintf().

--- diff/drivers/md/dm-io.c	2004-02-27 11:10:41.000000000 +0000
+++ source/drivers/md/dm-io.c	2004-03-01 11:49:42.000000000 +0000
@@ -58,11 +58,7 @@ static void bio_set_exit(struct bio_set 
 
 static void mk_name(char *str, size_t len, const char *prefix, unsigned count)
 {
-	int r;
-
-	r = snprintf(str, len, "%s-%u", prefix, count);
-	if (r < 0)
-		str[len - 1] = '\0';
+	snprintf(str, len, "%s-%u", prefix, count);
 }
 
 static int bio_set_init(struct bio_set *bs, const char *slab_prefix,
@@ -75,7 +71,6 @@ static int bio_set_init(struct bio_set *
 	};
 
 
-	int r;
 	unsigned i, size;
 	struct biovec_pool *bp;
 
@@ -85,9 +80,7 @@ static int bio_set_init(struct bio_set *
 	/*
 	 * Set up the bio pool.
 	 */
-	r = snprintf(bs->name, sizeof(bs->name), "%s-bio", slab_prefix);
-	if (r < 0)
-		bs->name[sizeof(bs->name) - 1] = '\0';
+	snprintf(bs->name, sizeof(bs->name), "%s-bio", slab_prefix);
 
 	bs->bio_slab = kmem_cache_create(bs->name, sizeof(struct bio), 0,
 					 SLAB_HWCACHE_ALIGN, NULL, NULL);