nilfs2: add omitted comments for different structures in driver implementation

Add omitted comments for different structures in driver implementation.

Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/nilfs2/ifile.c b/fs/nilfs2/ifile.c
index 5a48df7..d8e65bd 100644
--- a/fs/nilfs2/ifile.c
+++ b/fs/nilfs2/ifile.c
@@ -29,7 +29,11 @@
 #include "alloc.h"
 #include "ifile.h"
 
-
+/**
+ * struct nilfs_ifile_info - on-memory private data of ifile
+ * @mi: on-memory private data of metadata file
+ * @palloc_cache: persistent object allocator cache of ifile
+ */
 struct nilfs_ifile_info {
 	struct nilfs_mdt_info mi;
 	struct nilfs_palloc_cache palloc_cache;