struct file_ra_state

https://elixir.bootlin.com/linux/v5.7/source/include/linux/fs.h#L918

/*
 * Track a single file's readahead state
 */
struct file_ra_state {
	pgoff_t start;			/* where readahead started */
	unsigned int size;		/* # of readahead pages */
	unsigned int async_size;	/* do asynchronous readahead when
					   there are only # of pages ahead */

	unsigned int ra_pages;		/* Maximum readahead window */
	unsigned int mmap_miss;		/* Cache miss stat for mmap accesses */
	loff_t prev_pos;		/* Cache last read() position */
};