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Subject[PATCH 1/9] memcg: memory hotpluf 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.


Signed-off-by: KAMEZAWA Hiruyoki <kamezawa.hiroyu@jp.fujitsu.com>

---
mm/page_cgroup.c | 43 +++++++++++++++++++++++++++++--------------
mm/slub.c | 6 ++++--
2 files changed, 33 insertions(+), 16 deletions(-)
Index: mmotm-2.6.28-Nov13/mm/page_cgroup.c
===================================================================
--- mmotm-2.6.28-Nov13.orig/mm/page_cgroup.c
+++ mmotm-2.6.28-Nov13/mm/page_cgroup.c
@@ -104,19 +104,29 @@ int __meminit init_section_page_cgroup(u
unsigned long table_size;
int nid, index;

- 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) {
@@ -204,18 +214,23 @@ static int page_cgroup_callback(struct n
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;
}

Index: mmotm-2.6.28-Nov13/mm/slub.c
===================================================================
--- mmotm-2.6.28-Nov13.orig/mm/slub.c
+++ mmotm-2.6.28-Nov13/mm/slub.c
@@ -3220,8 +3220,10 @@ static int slab_memory_callback(struct n
case MEM_CANCEL_OFFLINE:
break;
}
-
- ret = notifier_from_errno(ret);
+ if (ret)
+ ret = notifier_from_errno(ret);
+ else
+ ret = NOTIFY_OK;
return ret;
}



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