The default is to attempt to cache ie try to request oplock on files opened by the client (forcedirectio is off). Foredirectio also can indirectly alter the network read and write size, since i/o will now match what was requested by the application, as readahead and writebehind is not being performed by the page cache when forcedirectio is enabled for a mount

Code:
mount -t cifs //storage/path2 -o username=USER,password=PASSWORD,rw,bg,vers=3,proto=tcp,hard,intr,rsize=32768,wsize=32768,forcedirectio,llock /data2
Refer mount.cifs man page, docs stored at Documentation/filesystems/cifs.txt and fs/cifs/README in the linux kernel source tree for additional options and information.