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

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Date:   Wed, 26 Jan 2022 13:11:54 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chen Wandun <chenwandun@...wei.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, guillaume.tucker@...labora.com
Subject: Re: [PATCH] Revert "mm/page_isolation: unset migratetype directly
 for non Buddy page"

On Mon, Jan 17, 2022 at 10:27:12PM +0800, Chen Wandun wrote:
> This reverts commit 075782149abff45ee22f27315eced44d02b96779.
> 
> commit 075782149abf ("mm/page_isolation: unset migratetype directly for
> 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>

I see a number of qemu emulations fail with memory allocation
errors in v5.17-rc1. This revert fixes the problem.

Tested-by: Guenter Roeck <linux@...ck-us.net>

Guenter

> ---
>  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);
>  	}
> -- 
> 2.18.0.huawei.25
> 
>