linux-kernel - Re: [PATCH 2/3] mm/page_ext: remove rollback for untouched mem_section in online_page

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Message-Id: <20230714105422.648d17f9ba6141f26e469423@linux-foundation.org>
Date:   Fri, 14 Jul 2023 10:54:22 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kemeng Shi <shikemeng@...weicloud.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm/page_ext: remove rollback for untouched
 mem_section in online_page_ext

On Fri, 14 Jul 2023 19:47:48 +0800 Kemeng Shi <shikemeng@...weicloud.com> wrote:

> If init_section_page_ext failed, we only need rollback for mem_section
> before failed mem_section. Make rollback end point to failed mem_section
> to remove unnecessary rollback.
> 
> As pfn += PAGES_PER_SECTION will be executed even if init_section_page_ext
> failed. So pfn points to mem_section after failed mem_section. Subtract
> one mem_section from pfn to get failed mem_section.
> 
> ...
>
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -424,6 +424,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
>  		return 0;
>  
>  	/* rollback */
> +	end = pfn - PAGES_PER_SECTION;
>  	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
>  		__free_page_ext(pfn);
>  

This is a bugfix, yes?

I guess init_section_page_ext() never fails for anyone...