lowmemorykiller: Account for highmem during kswapd reclaim

Currently 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: 17626969
Change-Id: I938644584f374763d10d429d835e74daa4854a38
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>

drivers/staging/android/lowmemorykiller.c

@@ -161,6 +161,35 @@ 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;
@@ -171,6 +200,8 @@ 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);