smalloc: alloc failure cleanups

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/diskutil.c b/diskutil.c
index 3681dde..e29d1c3 100644
--- a/diskutil.c
+++ b/diskutil.c
@@ -281,6 +281,11 @@
 	dprint(FD_DISKUTIL, "add maj/min %d/%d: %s\n", majdev, mindev, path);
 
 	du = smalloc(sizeof(*du));
+	if (!du) {
+		log_err("fio: smalloc() pool exhausted\n");
+		return NULL;
+	}
+
 	memset(du, 0, sizeof(*du));
 	INIT_FLIST_HEAD(&du->list);
 	l = snprintf(du->path, sizeof(du->path), "%s/stat", path);