Re: [PATCH v1 06/11] mm/memory_hotplug: drop nr_isolate_pageblock in offline_pages()

[Michal Hocko <mhocko@suse.com>]

On Wed 19-08-20 12:11:52, David Hildenbrand wrote:
> We make sure that we cannot have any memory holes right at the beginning
> of offline_pages() and we only support to online/offline full sections.
> Both, sections and pageblocks are a power of two in size, and sections
> always span full pageblocks.
> 
> We can directly calculate the number of isolated pageblocks from nr_pages.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Signed-off-by: David Hildenbrand <david@redhat.com>

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

> ---
>  mm/memory_hotplug.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 50aa5df696e9d..098361fcb4504 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1460,10 +1460,10 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  {
>  	const unsigned long end_pfn = start_pfn + nr_pages;
>  	unsigned long pfn, system_ram_pages = 0;
> -	int ret, node, nr_isolate_pageblock;
>  	unsigned long flags;
>  	struct zone *zone;
>  	struct memory_notify arg;
> +	int ret, node;
>  	char *reason;
>  
>  	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
> @@ -1507,7 +1507,6 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  		reason = "failure to isolate range";
>  		goto failed_removal;
>  	}
> -	nr_isolate_pageblock = ret;
>  
>  	arg.start_pfn = start_pfn;
>  	arg.nr_pages = nr_pages;
> @@ -1569,7 +1568,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  	 * pageblocks zone counter here.
>  	 */
>  	spin_lock_irqsave(&zone->lock, flags);
> -	zone->nr_isolate_pageblock -= nr_isolate_pageblock;
> +	zone->nr_isolate_pageblock -= nr_pages / pageblock_nr_pages;
>  	spin_unlock_irqrestore(&zone->lock, flags);
>  
>  	/* removal success */
> -- 
> 2.26.2
> 

-- 
Michal Hocko
SUSE Labs