diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
index 3c040c81c77d..08a20e5bcf7f 100644
--- a/fs/nfsd/blocklayout.c
+++ b/fs/nfsd/blocklayout.c
@@ -147,8 +147,7 @@ nfsd4_block_get_device_info_simple(struct super_block *sb,
 	struct pnfs_block_deviceaddr *dev;
 	struct pnfs_block_volume *b;
 
-	dev = kzalloc(sizeof(struct pnfs_block_deviceaddr) +
-		      sizeof(struct pnfs_block_volume), GFP_KERNEL);
+	dev = kzalloc(struct_size(dev, volumes, 1), GFP_KERNEL);
 	if (!dev)
 		return -ENOMEM;
 	gdp->gd_device = dev;
@@ -255,8 +254,7 @@ nfsd4_block_get_device_info_scsi(struct super_block *sb,
 	const struct pr_ops *ops;
 	int ret;
 
-	dev = kzalloc(sizeof(struct pnfs_block_deviceaddr) +
-		      sizeof(struct pnfs_block_volume), GFP_KERNEL);
+	dev = kzalloc(struct_size(dev, volumes, 1), GFP_KERNEL);
 	if (!dev)
 		return -ENOMEM;
 	gdp->gd_device = dev;
diff --git a/fs/nfsd/blocklayoutxdr.h b/fs/nfsd/blocklayoutxdr.h
index b0361e8aa9a7..4e28ac8f1127 100644
--- a/fs/nfsd/blocklayoutxdr.h
+++ b/fs/nfsd/blocklayoutxdr.h
@@ -47,7 +47,7 @@ struct pnfs_block_volume {
 
 struct pnfs_block_deviceaddr {
 	u32				nr_volumes;
-	struct pnfs_block_volume	volumes[];
+	struct pnfs_block_volume	volumes[] __counted_by(nr_volumes);
 };
 
 __be32 nfsd4_block_encode_getdeviceinfo(struct xdr_stream *xdr,