Merge branch 'akpm' (patches from Andrew)

Merge various fixes from Andrew Morton:
 "10 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm, page_alloc: recalculate the preferred zoneref if the context can ignore memory policies
  mm, page_alloc: reset zonelist iterator after resetting fair zone allocation policy
  mm, oom_reaper: do not use siglock in try_oom_reaper()
  mm, page_alloc: prevent infinite loop in buffered_rmqueue()
  checkpatch: reduce git commit description style false positives
  mm/z3fold.c: avoid modifying HEADLESS page and minor cleanup
  memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem()
  mm: check the return value of lookup_page_ext for all call sites
  kdump: fix dmesg gdbmacro to work with record based printk
  mm: fix overflow in vm_map_ram()

1 files changed, 28 insertions, 11 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8f3bfc435ee..6903b695ebae 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -656,6 +656,9 @@ static inline void set_page_guard(struct zone *zone, struct page *page,
                 return;
 
         page_ext = lookup_page_ext(page);
+        if (unlikely(!page_ext))
+                return;
+
         __set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
 
         INIT_LIST_HEAD(&page->lru);
@@ -673,6 +676,9 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
                 return;
 
         page_ext = lookup_page_ext(page);
+        if (unlikely(!page_ext))
+                return;
+
         __clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
 
         set_page_private(page, 0);
@@ -2609,11 +2615,12 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
                                 page = list_last_entry(list, struct page, lru);
                         else
                                 page = list_first_entry(list, struct page, lru);
-                } while (page && check_new_pcp(page));
 
-                __dec_zone_state(zone, NR_ALLOC_BATCH);
-                list_del(&page->lru);
-                pcp->count--;
+                        __dec_zone_state(zone, NR_ALLOC_BATCH);
+                        list_del(&page->lru);
+                        pcp->count--;
+
+                } while (check_new_pcp(page));
         } else {
                 /*
                  * We most definitely don't want callers attempting to
@@ -3023,6 +3030,7 @@ reset_fair:
                 apply_fair = false;
                 fair_skipped = false;
                 reset_alloc_batches(ac->preferred_zoneref->zone);
+                z = ac->preferred_zoneref;
                 goto zonelist_scan;
         }
 
@@ -3596,6 +3604,17 @@ retry:
          */
         alloc_flags = gfp_to_alloc_flags(gfp_mask);
 
+        /*
+         * Reset the zonelist iterators if memory policies can be ignored.
+         * These allocations are high priority and system rather than user
+         * orientated.
+         */
+        if ((alloc_flags & ALLOC_NO_WATERMARKS) || !(alloc_flags & ALLOC_CPUSET)) {
+                ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);
+                ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+                                        ac->high_zoneidx, ac->nodemask);
+        }
+
         /* This is the last chance, in general, before the goto nopage. */
         page = get_page_from_freelist(gfp_mask, order,
                                 alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
@@ -3604,12 +3623,6 @@ retry:
 
         /* Allocate without watermarks if the context allows */
         if (alloc_flags & ALLOC_NO_WATERMARKS) {
-                /*
-                 * Ignore mempolicies if ALLOC_NO_WATERMARKS on the grounds
-                 * the allocation is high priority and these type of
-                 * allocations are system rather than user orientated
-                 */
-                ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);
                 page = get_page_from_freelist(gfp_mask, order,
                                                 ALLOC_NO_WATERMARKS, ac);
                 if (page)
@@ -3808,7 +3821,11 @@ retry_cpuset:
         /* Dirty zone balancing only done in the fast path */
         ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);
 
-        /* The preferred zone is used for statistics later */
+        /*
+         * The preferred zone is used for statistics but crucially it is
+         * also used as the starting point for the zonelist iterator. It
+         * may get reset for allocations that ignore memory policies.
+         */
         ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
                                         ac.high_zoneidx, ac.nodemask);
         if (!ac.preferred_zoneref) {