mm/readahead.c: fix incorrect comments for get_init_ra_size

In fact, formated values returned by get_init_ra_size are not that
intuitive.  This patch make the comments reflect its truth.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Lin Feng <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/readahead.c

@@ -309,7 +309,7 @@ void force_page_cache_ra(struct readahead_control *ractl,
  * Set the initial window size, round to next power of 2 and square
  * for small size, x 4 for medium, and x 2 for large
  * for 128k (32 page) max ra
- * 1-8 page = 32k initial, > 8 page = 128k initial
+ * 1-2 page = 16k, 3-4 page 32k, 5-8 page = 64k, > 8 page = 128k initial
  */
 static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
 {