lowmemorykiller: Account for highmem during kswapd reclaim

Currenlty most memory reclaim is done through kswapd.
Since kswapd uses a gfp mask of GFP_KERNEL, and because
the lowmemorykiller is zone aware, the lowmemorykiller will
ignore highmem most of the time.
This results in the lowmemorykiller being overly aggressive.

The fix to this issue is to allow the lowmemorykiller to
count highmem when being called by the kswapd if the lowmem
watermarks are satisfied.

Bug: 17494249
Change-Id: I5fd3895ce242ccac0e777b003c3893685e061ff3
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>

drivers/staging/android/lowmemorykiller.c

@@ -153,6 +153,35 @@ void tune_lmk_zone_param(struct zonelist *zonelist, int classzone_idx,
 	}
 }
 
+#ifdef CONFIG_HIGHMEM
+void adjust_gfp_mask(gfp_t *gfp_mask)
+{
+	struct zone *preferred_zone;
+	struct zonelist *zonelist;
+	enum zone_type high_zoneidx;
+
+	if (current_is_kswapd()) {
+		zonelist = node_zonelist(0, *gfp_mask);
+		high_zoneidx = gfp_zone(*gfp_mask);
+		first_zones_zonelist(zonelist, high_zoneidx, NULL,
+				&preferred_zone);
+
+		if (high_zoneidx == ZONE_NORMAL) {
+			if (zone_watermark_ok_safe(preferred_zone, 0,
+					high_wmark_pages(preferred_zone), 0,
+					0))
+				*gfp_mask |= __GFP_HIGHMEM;
+		} else if (high_zoneidx == ZONE_HIGHMEM) {
+			*gfp_mask |= __GFP_HIGHMEM;
+		}
+	}
+}
+#else
+void adjust_gfp_mask(gfp_t *unused)
+{
+}
+#endif
+
 void tune_lmk_param(int *other_free, int *other_file, struct shrink_control *sc)
 {
 	gfp_t gfp_mask;
@@ -163,6 +192,8 @@ void tune_lmk_param(int *other_free, int *other_file, struct shrink_control *sc)
 	int use_cma_pages;
 
 	gfp_mask = sc->gfp_mask;
+	adjust_gfp_mask(&gfp_mask);
+
 	zonelist = node_zonelist(0, gfp_mask);
 	high_zoneidx = gfp_zone(gfp_mask);
 	first_zones_zonelist(zonelist, high_zoneidx, NULL, &preferred_zone);