mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator

Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts
of memory when booting a secondary kernel.  Srikar Dronamraju reported
that multiple nodes may have no memory managed by the buddy allocator
but still return true for populated_zone().

Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of
nodes") was reported to cause kswapd to spin at 100% CPU usage when
fadump was enabled.  The old code happened to deal with the situation of
a populated node with zero free pages by co-incidence but the current
code tries to reclaim populated zones without realising that is
impossible.

We cannot just convert populated_zone() as many existing users really
need to check for present_pages.  This patch introduces a managed_zone()
helper and uses it in the few cases where it is critical that the check
is made for managed pages -- zonelist construction and page reclaim.

Link: http://lkml.kernel.org/r/20160831195104.GB8119@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 374d95d04178..b1e12a1ea9cf 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1665,7 +1665,7 @@ static bool inactive_reclaimable_pages(struct lruvec *lruvec,
 
         for (zid = sc->reclaim_idx; zid >= 0; zid--) {
                 zone = &pgdat->node_zones[zid];
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 if (zone_page_state_snapshot(zone, NR_ZONE_LRU_BASE +
@@ -2036,7 +2036,7 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
                 struct zone *zone = &pgdat->node_zones[zid];
                 unsigned long inactive_zone, active_zone;
 
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 inactive_zone = zone_page_state(zone,
@@ -2171,7 +2171,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 
                 for (z = 0; z < MAX_NR_ZONES; z++) {
                         struct zone *zone = &pgdat->node_zones[z];
-                        if (!populated_zone(zone))
+                        if (!managed_zone(zone))
                                 continue;
 
                         total_high_wmark += high_wmark_pages(zone);
@@ -2510,7 +2510,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
         /* If compaction would go ahead or the allocation would succeed, stop */
         for (z = 0; z <= sc->reclaim_idx; z++) {
                 struct zone *zone = &pgdat->node_zones[z];
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
@@ -2840,7 +2840,7 @@ static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
 
         for (i = 0; i <= ZONE_NORMAL; i++) {
                 zone = &pgdat->node_zones[i];
-                if (!populated_zone(zone) ||
+                if (!managed_zone(zone) ||
                     pgdat_reclaimable_pages(pgdat) == 0)
                         continue;
 
@@ -3141,7 +3141,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
         for (i = 0; i <= classzone_idx; i++) {
                 struct zone *zone = pgdat->node_zones + i;
 
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 if (!zone_balanced(zone, order, classzone_idx))
@@ -3169,7 +3169,7 @@ static bool kswapd_shrink_node(pg_data_t *pgdat,
         sc->nr_to_reclaim = 0;
         for (z = 0; z <= sc->reclaim_idx; z++) {
                 zone = pgdat->node_zones + z;
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
@@ -3242,7 +3242,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
                 if (buffer_heads_over_limit) {
                         for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
                                 zone = pgdat->node_zones + i;
-                                if (!populated_zone(zone))
+                                if (!managed_zone(zone))
                                         continue;
 
                                 sc.reclaim_idx = i;
@@ -3262,7 +3262,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
                  */
                 for (i = classzone_idx; i >= 0; i--) {
                         zone = pgdat->node_zones + i;
-                        if (!populated_zone(zone))
+                        if (!managed_zone(zone))
                                 continue;
 
                         if (zone_balanced(zone, sc.order, classzone_idx))
@@ -3508,7 +3508,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
         pg_data_t *pgdat;
         int z;
 
-        if (!populated_zone(zone))
+        if (!managed_zone(zone))
                 return;
 
         if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
@@ -3522,7 +3522,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
         /* Only wake kswapd if all zones are unbalanced */
         for (z = 0; z <= classzone_idx; z++) {
                 zone = pgdat->node_zones + z;
-                if (!populated_zone(zone))
+                if (!managed_zone(zone))
                         continue;
 
                 if (zone_balanced(zone, order, classzone_idx))