+ * Given 'z' scanning a zonelist, run a couple of quick checks to see
+ * if it is worth looking at further for free memory:
+ * 1) Check that the zone isn't thought to be full (doesn't have its
+ * bit set in the zonelist_cache fullzones BITMAP).
+ * 2) Check that the zones node (obtained from the zonelist_cache
+ * z_to_n[] mapping) is allowed in the passed in allowednodes mask.
+ * Return true (non-zero) if zone is worth looking at further, or
+ * else return false (zero) if it is not.
+ *
+ * This check -ignores- the distinction between various watermarks,
+ * such as GFP_HIGH, GFP_ATOMIC, PF_MEMALLOC, ... If a zone is
+ * found to be full for any variation of these watermarks, it will
+ * be considered full for up to one second by all requests, unless
+ * we are so low on memory on all allowed nodes that we are forced
+ * into the second scan of the zonelist.
+ *
+ * In the second scan we ignore this zonelist cache and exactly
+ * apply the watermarks to all zones, even it is slower to do so.
+ * We are low on memory in the second scan, and should leave no stone
+ * unturned looking for a free page.
+ */
+static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zone **z,
+ nodemask_t *allowednodes)
+{
+ struct zonelist_cache *zlc; /* cached zonelist speedup info */
+ int i; /* index of *z in zonelist zones */
+ int n; /* node that zone *z is on */
+
+ zlc = zonelist->zlcache_ptr;
+ if (!zlc)
+ return 1;
+
+ i = z - zonelist->zones;
+ n = zlc->z_to_n[i];
+
+ /* This zone is worth trying if it is allowed but not full */
+ return node_isset(n, *allowednodes) && !test_bit(i, zlc->fullzones);
+}
+
+/*
+ * Given 'z' scanning a zonelist, set the corresponding bit in
+ * zlc->fullzones, so that subsequent attempts to allocate a page
+ * from that zone don't waste time re-examining it.
+ */
+static void zlc_mark_zone_full(struct zonelist *zonelist, struct zone **z)
+{
+ struct zonelist_cache *zlc; /* cached zonelist speedup info */
+ int i; /* index of *z in zonelist zones */
+
+ zlc = zonelist->zlcache_ptr;
+ if (!zlc)
+ return;
+
+ i = z - zonelist->zones;
+
+ set_bit(i, zlc->fullzones);
+}
+
+#else /* CONFIG_NUMA */
+
+static nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
+{
+ return NULL;
+}
+
+static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zone **z,
+ nodemask_t *allowednodes)
+{
+ return 1;
+}
+
+static void zlc_mark_zone_full(struct zonelist *zonelist, struct zone **z)
+{
+}
+#endif /* CONFIG_NUMA */
+
+/*
+ * get_page_from_freelist goes through the zonelist trying to allocate