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Message-ID: <8a23c1b4-494e-1006-ee8c-e27a798d9f8f@huawei.com>
Date: Thu, 15 Sep 2022 16:11:25 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: Oscar Salvador <osalvador@...e.de>
CC: <akpm@...ux-foundation.org>, <david@...hat.com>,
<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/16] mm/page_alloc: add missing is_migrate_isolate()
check in set_page_guard()
On 2022/9/15 15:26, Oscar Salvador wrote:
> On Fri, Sep 09, 2022 at 05:24:43PM +0800, Miaohe Lin wrote:
>> In MIGRATE_ISOLATE case, zone freepage state shouldn't be modified as
>> caller will take care of it. Add missing is_migrate_isolate() here to
>> avoid possible unbalanced freepage state.
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>
> Ok, I gave it some thought and I guess it's safe to assume that this would happen if
> someone isolates the block, and then we face an MCE failure/soft-offline on a page
> within that block.
>
> take_page_off_buddy
> break_down_buddy_pages
> set_page_guard
>
> will trigger __mod_zone_freepage_state(), which already had been triggered back
> when the block was isolated.
>
> I think the changelog could grow fatter to better explain the issue.
That will be really helpful. Will do it in v2.
>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
Many thanks for your suggestion and review.
Thanks,
Miaohe Lin
>
>> ---
>> mm/page_alloc.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index a35ef385d906..94baf33da865 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -873,7 +873,8 @@ static inline bool set_page_guard(struct zone *zone, struct page *page,
>> INIT_LIST_HEAD(&page->buddy_list);
>> set_page_private(page, order);
>> /* Guard pages are not available for any usage */
>> - __mod_zone_freepage_state(zone, -(1 << order), migratetype);
>> + if (!is_migrate_isolate(migratetype))
>> + __mod_zone_freepage_state(zone, -(1 << order), migratetype);
>>
>> return true;
>> }
>> --
>> 2.23.0
>>
>
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