diff --git a/WHATS_NEW_DM b/WHATS_NEW_DM
index 4069bf10c..4062baf5d 100644
--- a/WHATS_NEW_DM
+++ b/WHATS_NEW_DM
@@ -1,5 +1,6 @@
 Version 1.02.23 - 
 ==================================
+  Define DM_READ_AHEAD_AUTO and DM_READ_AHEAD_NONE.
   Fix configure --with-dmeventd-path substitution.
   Allow $DM_DEV_DIR envvar to override default of "/dev".
   Create e.g., libdevmapper.so.1.02, in build dir alongside the .so file.
diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h
index a00345b49..3b79f1767 100644
--- a/libdm/libdevmapper.h
+++ b/libdm/libdevmapper.h
@@ -141,6 +141,9 @@ struct dm_deps *dm_task_get_deps(struct dm_task *dmt);
 struct dm_names *dm_task_get_names(struct dm_task *dmt);
 struct dm_versions *dm_task_get_versions(struct dm_task *dmt);
 
+#define DM_READ_AHEAD_AUTO UINT32_MAX	/* Use kernel default readahead */
+#define DM_READ_AHEAD_NONE 0		/* Disable readahead */
+
 int dm_task_set_ro(struct dm_task *dmt);
 int dm_task_set_newname(struct dm_task *dmt, const char *newname);
 int dm_task_set_minor(struct dm_task *dmt, int minor);