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

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Message-ID: <b1966d11-e874-c71e-d14f-c0c88ace297e@suse.cz>
Date:   Tue, 25 Jan 2022 17:40:18 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Chen Wandun <chenwandun@...wei.com>, 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"

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

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.

> ---
>  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);
>  	}