linux-kernel - Re: [PATCH] mm, memory_hotplug: teach has_unmovable

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Date:   Mon, 5 Nov 2018 10:35:50 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Stable tree <stable@...r.kernel.org>
Subject: Re: [PATCH] mm, memory_hotplug: teach has_unmovable_pages about of
 LRU migrateable pages

On Mon 05-11-18 17:26:18, Baoquan He wrote:
[...]
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a919ba5..021e39d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7824,7 +7824,8 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
>                 if (__PageMovable(page))
>                         continue;
> 
> -               if (!PageLRU(page))
> +               if (!PageLRU(page) &&
> +                       (get_pageblock_migratetype(page) != MIGRATE_MOVABLE))
>                         found++;
>                 /*
>                  * If there are RECLAIMABLE pages, we need to check

As explained during the private conversion I am not really thrilled by
this check. AFAIU this will be the case for basically all pages in the
zone_movable. As we have seen already some unexpected ones can lurk in
easily.

-- 
Michal Hocko
SUSE Labs