From: Larry Woodman <lwoodman@redhat.com>
Date: Mon, 18 Feb 2008 15:18:16 -0500
Subject: [mm] fix /proc/sys/vm/lowmem_reserve_ratio
Message-id: 1203365896.8054.16.camel@dhcp83-56.boston.redhat.com
O-Subject: [RHEL5-U3 patch] Problem with /proc/sys/vm/lowmem_reserve_ratio
Bugzilla: 457471
RH-Acked-by: Jeff Moyer <jmoyer@redhat.com>

balance_pgdat() calls zone_watermark_ok() three times, the first call
passes a zero(0) in as the 4th argument.  This 4th argument is the
classzone_idx which is used as the index into the
zone->lowmem_reserve[] array.  Since setup_per_zone_lowmem_reserve()
always sets the zone->lowmem_reserve[0] = 0(because there is nothing
below the DMA zone), zone_watermark_ok() will not consider the
lowmem_reserve pages when zero is passed as the 4th arg.  This prevents
kswaps from running when it should because the lowmem_reserve is not
included in the test.  The fix is to pass the current index "i" as the
4th argument to zone_watermark_ok() instead of zero(0).

 mm/vmscan.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bdd76ee..ea3b83d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1151,7 +1151,7 @@ loop_again:
 				continue;
 
 			if (!zone_watermark_ok(zone, order, zone->pages_high,
-					       0, 0)) {
+					       i, 0)) {
 				end_zone = i;
 				goto scan;
 			}