There wouldn't be any logging by default, though you can turn on cifs auditing to logs of users opening shares.
If there were active sessions you could list users and open directories and files with:
cifs sessions *
If you include the user argument, the command displays information about the specified user, along with the names and access level of files that user has opened. If you use * as the specified user, the command lists all users.
Executing the command for user sam might produce output as follows: