diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 5a51151f680d6b0d552a80f549dfce0ede0d6b24..089aed57e0836342a461c6cb12d9e54207797009 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -878,12 +878,9 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
 					struct dm_target *ti,
 					struct dm_dirty_log *dl)
 {
-	size_t len;
-	struct mirror_set *ms = NULL;
-
-	len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
+	struct mirror_set *ms =
+		kzalloc(struct_size(ms, mirror, nr_mirrors), GFP_KERNEL);
 
-	ms = kzalloc(len, GFP_KERNEL);
 	if (!ms) {
 		ti->error = "Cannot allocate mirror context";
 		return NULL;