On 09/27/2012 10:32 PM, Ni zhan Chen wrote:

On 09/27/2012 02:47 PM, Lai Jiangshan wrote:

quoted

Currently memory_hotplug only manages the node_states[N_HIGH_MEMORY],
it forgets to manage node_states[N_NORMAL_MEMORY]. it causes
node_states[N_NORMAL_MEMORY] becomes stale.

We add check_nodemasks_changes_online() and check_nodemasks_changes_offline()
to detect whether node_states[N_HIGH_MEMORY] and node_states[N_NORMAL_MEMORY]
are changed while hotpluging.

Also add @status_change_nid_normal to struct memory_notify, thus
the memory hotplug callbacks know whether the node_states[N_NORMAL_MEMORY]
are changed.

I still don't understand why need care N_NORMAL_MEMORY here, could you explain
in details?

Hi, Chen

In short node_states[N_NORMAL_MEMORY] will become wrong in some situation.
many memory management code access to this node_states[N_NORMAL_MEMORY].

I will add more detail in the changelog in next round.

Thanks,
Lai

quoted

Signed-off-by: Lai Jiangshan <redacted>
---
  Documentation/memory-hotplug.txt |    5 ++-
  include/linux/memory.h           |    1 +
  mm/memory_hotplug.c              |   94 +++++++++++++++++++++++++++++++------
  3 files changed, 83 insertions(+), 17 deletions(-)

diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index 6d0c251..6e6cbc7 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt

@@ -377,15 +377,18 @@ The third argument is passed by pointer of struct memory_notify.
  struct memory_notify {
         unsigned long start_pfn;
         unsigned long nr_pages;
+       int status_change_nid_normal;
         int status_change_nid;
  }
    start_pfn is start_pfn of online/offline memory.
  nr_pages is # of pages of online/offline memory.
+status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask
+is (will be) set/clear, if this is -1, then nodemask status is not changed.
  status_change_nid is set node id when N_HIGH_MEMORY of nodemask is (will be)
  set/clear. It means a new(memoryless) node gets new memory by online and a
  node loses all memory. If this is -1, then nodemask status is not changed.
-If status_changed_nid >= 0, callback should create/discard structures for the
+If status_changed_nid* >= 0, callback should create/discard structures for the
  node if necessary.
    --------------

diff --git a/include/linux/memory.h b/include/linux/memory.h
index ff9a9f8..a09216d 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h

@@ -53,6 +53,7 @@ int arch_get_memory_phys_device(unsigned long start_pfn);
  struct memory_notify {
      unsigned long start_pfn;
      unsigned long nr_pages;
+    int status_change_nid_normal;
      int status_change_nid;
  };
  diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c

index 6a5b90d..b62d429b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -460,6 +460,34 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
      return 0;
  }
  +static void check_nodemasks_changes_online(unsigned long nr_pages,
+    struct zone *zone, struct memory_notify *arg)
+{
+    int nid = zone_to_nid(zone);
+    enum zone_type zone_last = ZONE_NORMAL;
+
+    if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
+        zone_last = ZONE_MOVABLE;
+
+    if (zone_idx(zone) <= zone_last && !node_state(nid, N_NORMAL_MEMORY))
+        arg->status_change_nid_normal = nid;
+    else
+        arg->status_change_nid_normal = -1;
+
+    if (!node_state(nid, N_HIGH_MEMORY))
+        arg->status_change_nid = nid;
+    else
+        arg->status_change_nid = -1;
+}
+
+static void set_nodemasks(int node, struct memory_notify *arg)
+{
+    if (arg->status_change_nid_normal >= 0)
+        node_set_state(node, N_NORMAL_MEMORY);
+
+    node_set_state(node, N_HIGH_MEMORY);
+}
+
    int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
  {

@@ -471,13 +499,18 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
      struct memory_notify arg;
        lock_memory_hotplug();
+    /*
+     * This doesn't need a lock to do pfn_to_page().
+     * The section can't be removed here because of the
+     * memory_block->state_mutex.
+     */
+    zone = page_zone(pfn_to_page(pfn));
+
      arg.start_pfn = pfn;
      arg.nr_pages = nr_pages;
-    arg.status_change_nid = -1;
+    check_nodemasks_changes_online(nr_pages, zone, &arg);
        nid = page_to_nid(pfn_to_page(pfn));
-    if (node_present_pages(nid) == 0)
-        arg.status_change_nid = nid;
        ret = memory_notify(MEM_GOING_ONLINE, &arg);
      ret = notifier_to_errno(ret);

@@ -487,12 +520,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
          return ret;
      }
      /*
-     * This doesn't need a lock to do pfn_to_page().
-     * The section can't be removed here because of the
-     * memory_block->state_mutex.
-     */
-    zone = page_zone(pfn_to_page(pfn));
-    /*
       * If this zone is not populated, then it is not in zonelist.
       * This means the page allocator ignores this zone.
       * So, zonelist must be updated after online.

@@ -517,7 +544,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
      zone->present_pages += onlined_pages;
      zone->zone_pgdat->node_present_pages += onlined_pages;
      if (onlined_pages) {
-        node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
+        set_nodemasks(zone_to_nid(zone), &arg);
          if (need_zonelists_rebuild)
              build_all_zonelists(NULL, zone);
          else

@@ -870,6 +897,44 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
      return offlined;
  }
  +static void check_nodemasks_changes_offline(unsigned long nr_pages,
+        struct zone *zone, struct memory_notify *arg)
+{
+    struct pglist_data *pgdat = zone->zone_pgdat;
+    unsigned long present_pages = 0;
+    enum zone_type zt, zone_last = ZONE_NORMAL;
+
+    if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
+        zone_last = ZONE_MOVABLE;
+
+    for (zt = 0; zt <= zone_last; zt++)
+        present_pages += pgdat->node_zones[zt].present_pages;
+    if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
+        arg->status_change_nid_normal = zone_to_nid(zone);
+    else
+        arg->status_change_nid_normal = -1;
+
+    zone_last = ZONE_MOVABLE;
+    for (; zt <= zone_last; zt++)
+        present_pages += pgdat->node_zones[zt].present_pages;
+    if (nr_pages >= present_pages)
+        arg->status_change_nid = zone_to_nid(zone);
+    else
+        arg->status_change_nid = -1;
+}
+
+static void clear_nodemasks(int node, struct memory_notify *arg)
+{
+    if (arg->status_change_nid_normal >= 0)
+        node_clear_state(node, N_NORMAL_MEMORY);
+
+    if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
+        return;
+
+    if (arg->status_change_nid >= 0)
+        node_clear_state(node, N_HIGH_MEMORY);
+}
+
  static int __ref offline_pages(unsigned long start_pfn,
            unsigned long end_pfn, unsigned long timeout)
  {

@@ -903,9 +968,7 @@ static int __ref offline_pages(unsigned long start_pfn,
        arg.start_pfn = start_pfn;
      arg.nr_pages = nr_pages;
-    arg.status_change_nid = -1;
-    if (nr_pages >= node_present_pages(node))
-        arg.status_change_nid = node;
+    check_nodemasks_changes_offline(nr_pages, zone, &arg);
        ret = memory_notify(MEM_GOING_OFFLINE, &arg);
      ret = notifier_to_errno(ret);

@@ -973,10 +1036,9 @@ repeat:
      if (!populated_zone(zone))
          zone_pcp_reset(zone);
  -    if (!node_present_pages(node)) {
-        node_clear_state(node, N_HIGH_MEMORY);
+    clear_nodemasks(node, &arg);
+    if (arg.status_change_nid >= 0)
          kswapd_stop(node);
-    }
        vm_total_pages = nr_free_pagecache_pages();
      writeback_set_ratelimit();

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