[patch] UBIFS: improved comment for data node's format history

[Joel Reardon]

A few more lines of comment on ksa_pos field in struct ubifs_data_node.

Signed-off-by: Joel Reardon <reardonj at inf.ethz.ch>
---
 fs/ubifs/ubifs-media.h |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index 55f2ccd..90f348c 100644
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -545,6 +545,11 @@ struct ubifs_dent_node {
  * @padding: reserved for future, zeroes
  * @data: data
  *
+ * The @ksa_pos value is used for secure deletion enhancement of UBIFS.
+ * In older versions of UBIFS, @ksa_pos did not exist but was instead an
+ * unused part of @key and was set to all zeros. UBIFS partitions with secure
+ * deletion disabled also store all zeros for ksa_pos.
+ *
  * Note, do not forget to amend 'zero_data_node_unused()' function when
  * changing the padding fields.
  */
-- 
1.7.5.4