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Date: Mon, 17 Nov 2008 13:30:08 -0800
From: Badari Pulavarty <pbadari@...ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.28-rc4 mem_cgroup_charge_common panic
On Fri, 2008-11-14 at 13:10 +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 13 Nov 2008 10:53:24 -0800
> Badari Pulavarty <pbadari@...ibm.com> wrote:
> > I tried mmtom + startpfn fix + this fix + notifier fix. Didn't help.
> > I am not using SLUB (using SLAB). Yes. I am testing "real" memory
> > remove (not just offline/online), since it executes more code of
> > freeing memmap etc.
> >
> > Code that is panicing is list_add() in mem_cgroup_add_list().
> > I will debug it further.
> >
>
> Considering difference between "real" memory hotplug and logical ones,
> I found this. I hope this fixes the bug.
> But I myself can't do test this..
>
> Thanks,
> -Kame
>
Kame,
With this patch I am able to run tests without any issues.
Sorry for delayed response, I wanted to make sure test runs fine over
the weekend.
Tested-by: Badari Pulavarty <pbadari@...ibm.com>
Thanks,
Badari
> ==
> 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 and
> we have to update that.
>
> But current MEM_ONLINE handler doesn't check it and update page_cgroup->page
> if it's not necessary to allocate page_cgroup.
>
> 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@...fujitsu.com>
>
> ---
> mm/page_cgroup.c | 39 +++++++++++++++++++++++++++------------
> mm/slub.c | 6 ++++--
> 2 files changed, 31 insertions(+), 14 deletions(-)
>
> Index: mmotm-2.6.28-Nov10/mm/page_cgroup.c
> ===================================================================
> --- mmotm-2.6.28-Nov10.orig/mm/page_cgroup.c
> +++ mmotm-2.6.28-Nov10/mm/page_cgroup.c
> @@ -104,18 +104,30 @@ int __meminit init_section_page_cgroup(u
> unsigned long table_size;
> int nid, index;
>
> - 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,
> + 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) {
> @@ -204,19 +216,22 @@ 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_GOING_OFFLINE:
> + case MEM_CANCEL_ONLINE:
> 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-Nov10/mm/slub.c
> ===================================================================
> --- mmotm-2.6.28-Nov10.orig/mm/slub.c
> +++ mmotm-2.6.28-Nov10/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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