linux-kernel - Re: [PATCH v1 03/11] mm/memory_hotplug: simplify checking if all pages are isolated in offline

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Date:   Wed, 19 Aug 2020 14:39:40 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Baoquan He <bhe@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH v1 03/11] mm/memory_hotplug: simplify checking if all
 pages are isolated in offline_pages()

On Wed 19-08-20 12:11:49, David Hildenbrand wrote:
> We make sure that we cannot have any memory holes right at the beginning
> of offline_pages(). We no longer need walk_system_ram_range() and can
> call test_pages_isolated() directly.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/memory_hotplug.c | 16 +---------------
>  1 file changed, 1 insertion(+), 15 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6856702af68d9..f64478349148d 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1384,17 +1384,6 @@ offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
>  	return 0;
>  }
>  
> -/*
> - * Check all pages in range, recorded as memory resource, are isolated.
> - */
> -static int
> -check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
> -			void *data)
> -{
> -	return test_pages_isolated(start_pfn, start_pfn + nr_pages,
> -				   MEMORY_OFFLINE);
> -}
> -
>  static int __init cmdline_parse_movable_node(char *p)
>  {
>  	movable_node_enabled = true;
> @@ -1579,10 +1568,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  			reason = "failure to dissolve huge pages";
>  			goto failed_removal_isolated;
>  		}
> -		/* check again */
> -		ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn,
> -					    NULL, check_pages_isolated_cb);
> -	} while (ret);
> +	} while (test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE));
>  
>  	/* Ok, all of our target is isolated.
>  	   We cannot do rollback at this point. */
> -- 
> 2.26.2

-- 
Michal Hocko
SUSE Labs