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Commit dc19f9db authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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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: default avatarKAMEZAWA 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: default avatarBadari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b29acbdc

mm/page_cgroup.c

+29 −14
Original line number Diff line number Diff line
@@ -107,20 +107,30 @@ int __init_refok init_section_page_cgroup(unsigned long pfn) 


	section = __pfn_to_section(pfn);



	if (section->page_cgroup)

		return 0;



	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,

			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) {

		printk(KERN_ERR "page cgroup allocation failure\n");
@@ -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;

	}



	if (ret)

		ret = notifier_from_errno(ret);

	else

		ret = NOTIFY_OK;



	return ret;

}

mm/slub.c

+4 −2
Original line number Diff line number Diff line
@@ -2931,8 +2931,10 @@ static int slab_memory_callback(struct notifier_block *self, 
	case MEM_CANCEL_OFFLINE:

		break;

	}



	if (ret)

		ret = notifier_from_errno(ret);

	else

		ret = NOTIFY_OK;

	return ret;

}