1 files changed, 35 insertions, 5 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 5c76737d836b..ae19af5ec02c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -474,10 +474,16 @@ struct zone {
          * frequently read in proximity to zone->lock.  It's good to
          * give them a chance of being in the same cacheline.
          *
-         * Write access to present_pages and managed_pages at runtime should
-         * be protected by lock_memory_hotplug()/unlock_memory_hotplug().
-         * Any reader who can't tolerant drift of present_pages and
-         * managed_pages should hold memory hotplug lock to get a stable value.
+         * Write access to present_pages at runtime should be protected by
+         * lock_memory_hotplug()/unlock_memory_hotplug().  Any reader who can't
+         * tolerant drift of present_pages should hold memory hotplug lock to
+         * get a stable value.
+         *
+         * Read access to managed_pages should be safe because it's unsigned
+         * long. Write access to zone->managed_pages and totalram_pages are
+         * protected by managed_page_count_lock at runtime. Idealy only
+         * adjust_managed_page_count() should be used instead of directly
+         * touching zone->managed_pages and totalram_pages.
          */
         unsigned long           spanned_pages;
         unsigned long           present_pages;
@@ -495,6 +501,13 @@ typedef enum {
         ZONE_CONGESTED,                 /* zone has many dirty pages backed by
                                          * a congested BDI
                                          */
+        ZONE_TAIL_LRU_DIRTY,            /* reclaim scanning has recently found
+                                         * many dirty file pages at the tail
+                                         * of the LRU.
+                                         */
+        ZONE_WRITEBACK,                 /* reclaim scanning has recently found
+                                         * many pages under writeback
+                                         */
 } zone_flags_t;
 
 static inline void zone_set_flag(struct zone *zone, zone_flags_t flag)
@@ -517,6 +530,16 @@ static inline int zone_is_reclaim_congested(const struct zone *zone)
         return test_bit(ZONE_CONGESTED, &zone->flags);
 }
 
+static inline int zone_is_reclaim_dirty(const struct zone *zone)
+{
+        return test_bit(ZONE_TAIL_LRU_DIRTY, &zone->flags);
+}
+
+static inline int zone_is_reclaim_writeback(const struct zone *zone)
+{
+        return test_bit(ZONE_WRITEBACK, &zone->flags);
+}
+
 static inline int zone_is_reclaim_locked(const struct zone *zone)
 {
         return test_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
@@ -716,7 +739,10 @@ typedef struct pglist_data {
          * or node_spanned_pages stay constant.  Holding this will also
          * guarantee that any pfn_valid() stays that way.
          *
-         * Nests above zone->lock and zone->size_seqlock.
+         * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
+         * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
+         *
+         * Nests above zone->lock and zone->span_seqlock
          */
         spinlock_t node_size_lock;
 #endif
@@ -1111,6 +1137,10 @@ struct mem_section {
         struct page_cgroup *page_cgroup;
         unsigned long pad;
 #endif
+        /*
+         * WARNING: mem_section must be a power-of-2 in size for the
+         * calculation and use of SECTION_ROOT_MASK to make sense.
+         */
 };
 
 #ifdef CONFIG_SPARSEMEM_EXTREME