diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index dfe29b29915fc..7c2ee0795dc70 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -313,7 +313,7 @@ static struct btrfs_delayed_item *btrfs_alloc_delayed_item(u16 data_len,
 {
 	struct btrfs_delayed_item *item;
 
-	item = kmalloc(sizeof(*item) + data_len, GFP_NOFS);
+	item = kmalloc(struct_size(item, data, data_len), GFP_NOFS);
 	if (item) {
 		item->data_len = data_len;
 		item->type = type;
diff --git a/fs/btrfs/delayed-inode.h b/fs/btrfs/delayed-inode.h
index dc1085b2a3976..1da213197f55f 100644
--- a/fs/btrfs/delayed-inode.h
+++ b/fs/btrfs/delayed-inode.h
@@ -95,7 +95,7 @@ struct btrfs_delayed_item {
 	bool logged;
 	/* The maximum leaf size is 64K, so u16 is more than enough. */
 	u16 data_len;
-	char data[];
+	char data[] __counted_by(data_len);
 };
 
 static inline void btrfs_init_delayed_root(