Lustre advise IOCTL interface can set the CEF_LOCK_NO_EXPAND flag, which tells the OSC (the per OST layer of the client) to set LDLM_FL_NO_EXPANSION on any lock requests. LDLM_FL_NO_EXPANSION is a new LDLM lock flag which tells the server not to expand the lock extent.

To set this parameter much easier for benchmark or debug purpose, It would better to add a tunable "llite.*.lock_no_expand" to control whether to expand the lock extent for I/O.