memcg: memory hotplug fix for notifier callback

Fixes for memcg/memory hotplug.

While memory hotplug allocate/free memmap, page_cgroup doesn't free
page_cgroup at OFFLINE when page_cgroup is allocated via bootomem.
(Because freeing bootmem requires special care.)

Then, if page_cgroup is allocated by bootmem and memmap is freed/allocated
by memory hotplug, page_cgroup->page == page is no longer true.

But current MEM_ONLINE handler doesn't check it and update
page_cgroup->page if it's not necessary to allocate page_cgroup.  (This
was not found because memmap is not freed if SPARSEMEM_VMEMMAP is y.)

And I noticed that MEM_ONLINE can be called against "part of section".
So, freeing page_cgroup at CANCEL_ONLINE will cause trouble.  (freeing
used page_cgroup) Don't rollback at CANCEL.

One more, current memory hotplug notifier is stopped by slub because it
sets NOTIFY_STOP_MASK to return vaule.  So, page_cgroup's callback never
be called.  (low priority than slub now.)

I think this slub's behavior is not intentional(BUG). and fixes it.

Another way to be considered about page_cgroup allocation:
  - free page_cgroup at OFFLINE even if it's from bootmem
    and remove specieal handler. But it requires more changes.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=12041

Signed-off-by: KAMEZAWA Hiruyoki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Tested-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 33 insertions, 16 deletions

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 436c00229e70..0b3cbf090a67 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -107,19 +107,29 @@ int __init_refok init_section_page_cgroup(unsigned long pfn)
 
         section = __pfn_to_section(pfn);
 
-        if (section->page_cgroup)
-                return 0;
-
-        nid = page_to_nid(pfn_to_page(pfn));
-
-        table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
-        if (slab_is_available()) {
-                base = kmalloc_node(table_size, GFP_KERNEL, nid);
-                if (!base)
-                        base = vmalloc_node(table_size, nid);
-        } else {
-                base = __alloc_bootmem_node_nopanic(NODE_DATA(nid), table_size,
+        if (!section->page_cgroup) {
+                nid = page_to_nid(pfn_to_page(pfn));
+                table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
+                if (slab_is_available()) {
+                        base = kmalloc_node(table_size, GFP_KERNEL, nid);
+                        if (!base)
+                                base = vmalloc_node(table_size, nid);
+                } else {
+                        base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
+                                table_size,
                                 PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
+                }
+        } else {
+                /*
+                 * We don't have to allocate page_cgroup again, but
+                 * address of memmap may be changed. So, we have to initialize
+                 * again.
+                 */
+                base = section->page_cgroup + pfn;
+                table_size = 0;
+                /* check address of memmap is changed or not. */
+                if (base->page == pfn_to_page(pfn))
+                        return 0;
         }
 
         if (!base) {
@@ -208,18 +218,23 @@ static int __meminit page_cgroup_callback(struct notifier_block *self,
                 ret = online_page_cgroup(mn->start_pfn,
                                    mn->nr_pages, mn->status_change_nid);
                 break;
-        case MEM_CANCEL_ONLINE:
         case MEM_OFFLINE:
                 offline_page_cgroup(mn->start_pfn,
                                 mn->nr_pages, mn->status_change_nid);
                 break;
+        case MEM_CANCEL_ONLINE:
         case MEM_GOING_OFFLINE:
                 break;
         case MEM_ONLINE:
         case MEM_CANCEL_OFFLINE:
                 break;
         }
-        ret = notifier_from_errno(ret);
+
+        if (ret)
+                ret = notifier_from_errno(ret);
+        else
+                ret = NOTIFY_OK;
+
         return ret;
 }
 
diff --git a/mm/slub.c b/mm/slub.c
index 7ad489af9561..749588a50a5a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2931,8 +2931,10 @@ static int slab_memory_callback(struct notifier_block *self,
         case MEM_CANCEL_OFFLINE:
                 break;
         }
-
-        ret = notifier_from_errno(ret);
+        if (ret)
+                ret = notifier_from_errno(ret);
+        else
+                ret = NOTIFY_OK;
         return ret;
 }