clarify when read_ahead may be set

diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h
index 7e9810a3303d9ffab0b37b2b6d6fd9829797ddda..ef2b5301b0f1d812edfa83f56186d24331597b56 100644 (file)
--- a/libdm/libdevmapper.h
+++ b/libdm/libdevmapper.h
@@ -165,6 +165,9 @@ int dm_task_suppress_identical_reload(struct dm_task *dmt);
 
 #define DM_READ_AHEAD_MINIMUM_FLAG     0x1     /* Value supplied is minimum */
 
+/*
+ * Read ahead is set with DM_DEVICE_CREATE with a table or DM_DEVICE_RESUME.
+ */
 int dm_task_set_read_ahead(struct dm_task *dmt, uint32_t read_ahead,
                           uint32_t read_ahead_flags);
 uint32_t dm_task_get_read_ahead(const struct dm_task *dmt,