Here are the data structures with brief descriptions:

Csession_cdev	The wrapper containing the char device used to manage sessions plus the kobject needed into the /sys to get info about the open sessions
Csession_file_node	This is the structure into the rb_tree that contains all the open files with their counter
Csession_priv_data	This structure is linked to the original file through the field private_data and the main purpose is to keep the pointer to the session file
Csession_proc_node	This is the structure into the rb_tree that contains all the processes which are currently using the sessions