include/linux/fs.h

405 	void (*readahead)(struct readahead_control *);
954  * struct file_ra_state - Track a file's readahead state.
955  * @start: Where the most recent readahead started.
956  * @size: Number of pages read in the most recent readahead.
958  *      and so were/are genuinely "ahead".  Start next readahead when
960  * @ra_pages: Maximum size of a readahead request, copied from the bdi.
964  * When this structure is passed to ->readahead(), the "most recent"
965  * readahead means the current readahead.
977  * Check if @index falls in the readahead windows.