diff --git a/fs/nilfs2/dat.c b/fs/nilfs2/dat.c
index 674380837ab9..888dc1831c86 100644
--- a/fs/nilfs2/dat.c
+++ b/fs/nilfs2/dat.c
@@ -524,6 +524,9 @@ int nilfs_dat_read(struct super_block *sb, size_t entry_size,
 	if (err)
 		goto failed;
 
+	err = nilfs_attach_btree_node_cache(dat);
+	if (err)
+		goto failed;
 	err = nilfs_read_inode_common(dat, raw_inode);
 	if (err)
 		goto failed;
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index e17b8da66491..e0a606643e87 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -736,6 +736,12 @@ static int nilfs_ioctl_mark_blocks_dirty(struct the_nilfs *nilfs,
 	int ret, i;
 
 	for (i = 0; i < nmembs; i++) {
+		/*
+		 * bd_oblocknr must never be 0 as block 0
+		 * is never a valid GC target block
+		 */
+		if (unlikely(!bdescs[i].bd_oblocknr))
+			return -EINVAL;
 		/* XXX: use macro or inline func to check liveness */
 		ret = nilfs_bmap_lookup_at_level(bmap,
 						 bdescs[i].bd_offset,