[PATCH 4/6] readahead: context based method: remove readahead_ratio

[Fengguang Wu <wfg@mail.ustc.edu.cn>]

[-- Attachment #1: readahead-context-based-method-remove-readahead_ratio.patch --]
[-- Type: text/plain, Size: 1104 bytes --]

The context based readahead is pretty conservative by nature,
so do not apply readahead_ratio here.

Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>

---
 mm/readahead.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- linux-2.6.20-rc3-mm1.orig/mm/readahead.c
+++ linux-2.6.20-rc3-mm1/mm/readahead.c
@@ -1236,9 +1236,7 @@ static unsigned long count_history_pages
 	 * Check the far pages coarsely.
 	 * The enlarged count will contribute to the look-ahead size.
 	 */
-	lookback = ra_max * (LOOKAHEAD_RATIO + 1) *
-						100 / (readahead_ratio | 1);
-
+	lookback = ra_max * LOOKAHEAD_RATIO;
 	for (count += ra_max; count < lookback; count += ra_max)
 		if (!__probe_page(mapping, offset - count))
 			break;
@@ -1384,7 +1382,8 @@ has_history_pages:
 		adjust_rala_aggressive(ra_max, &ra_size, &la_size);
 		ra_set_class(ra, RA_CLASS_CONTEXT_AGGRESSIVE);
 	} else {
-		ra_size = max(ra_min, ra_size * readahead_ratio / 100);
+		if (ra_size < ra_min)
+		    ra_size = ra_min;
 		if (!adjust_rala(ra_max, &ra_size, &la_size))
 			return -1;
 		ra_set_class(ra, RA_CLASS_CONTEXT);

--