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Subject: Re: [PATCH 5/6] mm/page_alloc.c: avoid accessing uninitialized pcp
 page migratetype
To:     Miaohe Lin <linmiaohe@huawei.com>
Cc:     akpm@linux-foundation.org, vbabka@suse.cz, sfr@canb.auug.org.au,
        peterz@infradead.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Mel Gorman <mgorman@techsingularity.net>
References: <20210830141051.64090-1-linmiaohe@huawei.com>
 <20210830141051.64090-6-linmiaohe@huawei.com>
 <20210831134311.GG4128@techsingularity.net>
 <877b7043-65c3-5e08-ac89-ad6f10e354b3@redhat.com>
 <f801cd23-6897-53c7-a689-2ade60578d7e@huawei.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Message-ID: <e7f834ec-5551-07d7-f439-7e20e4345389@redhat.com>
Date:   Wed, 1 Sep 2021 10:10:35 +0200
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On 01.09.21 10:02, Miaohe Lin wrote:
> On 2021/8/31 22:23, David Hildenbrand wrote:
>> On 31.08.21 15:43, Mel Gorman wrote:
>>> On Mon, Aug 30, 2021 at 10:10:50PM +0800, Miaohe Lin wrote:
>>>> If it's not prepared to free unref page, the pcp page migratetype is
>>>> unset. Thus We will get rubbish from get_pcppage_migratetype() and
>>>> might list_del &page->lru again after it's already deleted from the
>>>> list leading to grumble about data corruption.
>>>>
>>>> Fixes: 3dcbe270d8ec ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
>>>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>>>
>>> Acked-by: Mel Gorman <mgorman@techsingularity.net>
>>>
>>> This fix is fairly important. Take this patch out and send it on its own
>>> so it gets picked up relatively quickly. It does not belong in a series
>>> that is mostly cosmetic cleanups.
>>
>> I think the commit id is wrong. Shouldn't that be
>>
>> df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
>>
>> ?
>>
> 
> Many thanks for pointing this out.
> 
> I used to save the git log in a file to make life easier. But it seems this leads
> to the old commit id above.
> 
> commit 3dcbe270d8ec57e534f5c605279cdc3ceb1f044a
> Author: Mel Gorman <mgorman@techsingularity.net>
> Date:   Fri Jun 4 14:20:03 2021 +1000
> 
>      mm/page_alloc: avoid conflating IRQs disabled with zone->lock
> 
> git name-rev 3dcbe270d8ec
> 3dcbe270d8ec tags/next-20210604~2^2~196
> 
> vs
> 
> commit df1acc856923c0a65c28b588585449106c316b71
> Author: Mel Gorman <mgorman@techsingularity.net>
> Date:   Mon Jun 28 19:42:00 2021 -0700
> 
>      mm/page_alloc: avoid conflating IRQs disabled with zone->lock
> 
> git name-rev df1acc856923
> df1acc856923 tags/next-20210630~2^2~278
> 
> Their contents are same but with different commit id. The previous one
> could have been git-rebased.
> 

-mm tree commit ids keep changing until patches are upstream. Therefore, 
you can observe changing commit ids in -next. Always use the ones from 
Linus' tree, they are stable.

-- 
Thanks,

David / dhildenb