linux-kernel - Re: [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one

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Message-ID: <20210113105657.GA26599@linux>
Date:   Wed, 13 Jan 2021 11:57:01 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     mike.kravetz@...cle.com, akpm@...ux-foundation.org,
        n-horiguchi@...jp.nec.com, ak@...ux.intel.com, mhocko@...e.cz,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yang Shi <shy828301@...il.com>, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose
 refcount is one

On Wed, Jan 13, 2021 at 01:22:04PM +0800, Muchun Song wrote:
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 4385f2fb5d18..a6631c4eb6a6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  		return -ENOSYS;
>  	}
>  
> +	if (page_count(hpage) == 1) {
> +		/* page was freed from under us. So we are done. */
> +		putback_active_hugepage(hpage);
> +		return MIGRATEPAGE_SUCCESS;
> +	}
> +

I was a bit puzzled as why we did not go to the "goto" block that already does
this, but then I saw the put_new_page/new_hpage handlind further down.
It could be re-arranged but out of scope, so:

Reviewed-by: Oscar Salvador <osalvador@...e.de>


-- 
Oscar Salvador
SUSE L3