diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index adf6668..98bd0e9 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -120,6 +120,19 @@ struct ext4_ext_path {
 };
 
 /*
+ * Used to record a portion of a cluster found at the beginning or end
+ * of an extent while traversing the extent tree during space removal.
+ * A partial cluster may be removed if it does not contain blocks shared
+ * with extents that aren't being deleted (tofree state).  Otherwise,
+ * it cannot be removed (nofree state).
+ */
+struct partial_cluster {
+	ext4_fsblk_t pclu;  /* physical cluster number */
+	ext4_lblk_t lblk;   /* logical block number within logical cluster */
+	enum {initial, tofree, nofree} state;
+};
+
+/*
  * structure for external API
  */