WB_FRN_TIME_SHIFT  235 fs/fs-writeback.c #define WB_FRN_TIME_PERIOD	(2 * (1 << WB_FRN_TIME_SHIFT))	/* 2s */
WB_FRN_TIME_SHIFT  661 fs/fs-writeback.c 	max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,