linux-kernel - Re: [PATCH -rc7] mm/huge_memory: mark huge_zero

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Date: Wed, 15 May 2024 09:48:31 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: Yang Shi <shy828301@...il.com>, Andrew Morton <akpm@...ux-foundation.org>
CC: <nao.horiguchi@...il.com>, <xuyu@...ux.alibaba.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -rc7] mm/huge_memory: mark huge_zero_page reserved

On 2024/5/15 5:55, Yang Shi wrote:
> On Tue, May 14, 2024 at 3:42 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>>
>> On Tue, 14 May 2024 15:28:12 -0600 Yang Shi <shy828301@...il.com> wrote:
>>
>>> On Tue, May 14, 2024 at 3:14 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>>>>
>>>> On Sat, 11 May 2024 11:54:35 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:
>>>>
>>>>> When I did memory failure tests recently, below panic occurs:
>>>>>
>>>>>  kernel BUG at include/linux/mm.h:1135!
>>>>>  invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
>>>>>  CPU: 9 PID: 137 Comm: kswapd1 Not tainted 6.9.0-rc4-00491-gd5ce28f156fe-dirty #14
>>>>>
>>>>> ...
>>>>>
>>>>> --- a/mm/huge_memory.c
>>>>> +++ b/mm/huge_memory.c
>>>>> @@ -208,6 +208,7 @@ static bool get_huge_zero_page(void)
>>>>>               __free_pages(zero_page, compound_order(zero_page));
>>>>>               goto retry;
>>>>>       }
>>>>> +     __SetPageReserved(zero_page);
>>>>>       WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
>>>>>
>>>>>       /* We take additional reference here. It will be put back by shrinker */
>>>>> @@ -260,6 +261,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
>>>>>               struct page *zero_page = xchg(&huge_zero_page, NULL);
>>>>>               BUG_ON(zero_page == NULL);
>>>>>               WRITE_ONCE(huge_zero_pfn, ~0UL);
>>>>> +             __ClearPageReserved(zero_page);
>>>>>               __free_pages(zero_page, compound_order(zero_page));
>>>>>               return HPAGE_PMD_NR;
>>>>>       }
>>>>
>>>> This causes a bit of a mess when staged ahead of mm-stable.  So to
>>>> avoid disruption I staged it behind mm-stable.  This means that when
>>>> the -stable maintainers try to merge it, they will ask for a fixed up
>>>> version for older kernels so you can please just send them this
>>>> version.
>>>
>>> Can you please drop this from mm-unstable since both I and David
>>> nack'ed a similar patch in another thread.
>>> https://lore.kernel.org/linux-mm/20240511032801.1295023-1-linmiaohe@huawei.com/
>>
>> That appears to link to the incorrect email thread?
> 
> I meant that patch is actually same with this one. Just used folio
> interface instead of page. I'm not sure why Miaohe posted two. Maybe
> target to different version.

Sorry for causing confusion. These two patches really target to different branch.
This patch is for mainline and another one for mm-unstable.
Thanks both.
.