conduct checkpoint to reclaim the prefree segments
to free segments. By default, 100 segments, 200MB.
+ max_small_discards This parameter controls the number of discard
+ commands that consist small blocks less than 2MB.
+ The candidates to be discarded are cached until
+ checkpoint is triggered, and issued during the
+ checkpoint. By default, it is disabled with 0.
+
ipu_policy This parameter controls the policy of in-place
updates in f2fs. There are five policies:
0: F2FS_IPU_FORCE, 1: F2FS_IPU_SSR,