[PATCH 20/27] mm, vmscan: Update classzone_idx if buffer_heads_over_limit

[Mel Gorman]

If buffer heads are over the limit then the direct reclaim gfp_mask
is promoted to __GFP_HIGHMEM so that lowmem is indirectly freed. With
node-based reclaim, it is also required that the classzone_idx be updated
or the pages will be skipped.

Signed-off-by: Mel Gorman <mgor...@techsingularity.net>
Acked-by: Vlastimil Babka <vba...@suse.cz>
---
 mm/vmscan.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1f7c1262c0a3..f4c759b3581b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2571,8 +2571,10 @@ static void shrink_zones(struct zonelist *zonelist, 
struct scan_control *sc,
         * highmem pages could be pinning lowmem pages storing buffer_heads
         */
        orig_mask = sc->gfp_mask;
-       if (buffer_heads_over_limit)
+       if (buffer_heads_over_limit) {
                sc->gfp_mask |= __GFP_HIGHMEM;
+               classzone_idx = gfp_zone(sc->gfp_mask);
+       }
 
        for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                        gfp_zone(sc->gfp_mask), sc->nodemask) {
-- 
2.6.4