linux-kernel - Re: [PATCH] Revert "mm/page_isolation: unset migratetype directly for non Buddy page"

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Date:   Sun, 30 Jan 2022 10:24:43 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Chen Wandun <chenwandun@...wei.com>,
        Vlastimil Babka <vbabka@...e.cz>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        guillaume.tucker@...labora.com
Cc:     regressions@...ts.linux.dev, Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH] Revert "mm/page_isolation: unset migratetype directly for
 non Buddy page"

Hi, this is your Linux kernel regression tracker speaking.

On 26.01.22 03:18, Chen Wandun wrote:
> 在 2022/1/26 0:40, Vlastimil Babka 写道:
>> On 1/17/22 15:27, Chen Wandun wrote:
>>> This reverts commit 075782149abff45ee22f27315eced44d02b96779.
>>>
>>> commit 075782149abf ("mm/page_isolation: unset migratetype directly for
>> That's an old -next commit id, it went to mainline as 721fb891ad0b
>> ("mm/page_isolation: unset migratetype directly for non Buddy page")
>>
>>> non Buddy page") will result memory that should in buddy disappear by
>>> mistake. move_freepages_block move all pages in pageblock instead of
>>> pages indicated by input parameter, so if input pages is not in buddy
>>> but other pages in pageblock is in buddy, it will result in page out of
>>> control.
>>>
>>> Reported-by: "kernelci.org bot" <bot@...nelci.org>
>>> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
>> Acked-by: Vlastimil Babka <vbabka@...e.cz>
>>
>> #regzbot ^introduced: 721fb891ad0b

Thx for getting regzbot involved, much appreciated.

>> There should better be also:
>>
>> Fixes: 721fb891ad0b ("mm/page_isolation: unset migratetype directly
>> for non
>> Buddy page")
>>
>> Especially as that commit had a (inadequate, IMHO, for an optimization)
>> Fixes: tag and could end up being backported somewhere without the
>> followup
>> fix/revert.
>
> thanks, I will send v2

Just wondering:

Andrew, I don't see this patch in the list of changes you sent to Linus
yesterday. Shouldn't it be in there due to above reason alone? And there
is another reason: it seems to be an issue people actually hit, as
Guenter mentioned in this thread. It thus complicates things for those
that want to help testing pre-releases.

Or am I missing something/asking too much in this case?

BTW, let's tell regzbot about v2:

#regzbot monitor:
https://lore.kernel.org/all/20220126024436.13921-1-chenwandun@huawei.com/

Ciao, Thorsten

>>> ---
>>>   mm/page_isolation.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
>>> index 6a0ddda6b3c5..f67c4c70f17f 100644
>>> --- a/mm/page_isolation.c
>>> +++ b/mm/page_isolation.c
>>> @@ -115,7 +115,7 @@ static void unset_migratetype_isolate(struct page
>>> *page, unsigned migratetype)
>>>        * onlining - just onlined memory won't immediately be
>>> considered for
>>>        * allocation.
>>>        */
>>> -    if (!isolated_page && PageBuddy(page)) {
>>> +    if (!isolated_page) {
>>>           nr_pages = move_freepages_block(zone, page, migratetype,
>>> NULL);
>>>           __mod_zone_freepage_state(zone, nr_pages, migratetype);
>>>       }
>> .
> 
> 
>