linux-kernel - Re: [PATCH v1] mm/memory_hotplug: Easier calculation to get pages to next section boundary

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Message-ID: <20200206014642.GJ8965@MiWiFi-R3L-srv>
Date:   Thu, 6 Feb 2020 09:46:42 +0800
From:   Baoquan He <bhe@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        Wei Yang <richardw.yang@...ux.intel.com>
Subject: Re: [PATCH v1] mm/memory_hotplug: Easier calculation to get pages to
 next section boundary

On 02/05/20 at 02:52pm, David Hildenbrand wrote:
> Let's use a calculation that's easier to understand and calculates the
> same result. Reusing existing macros makes this look nicer.
> 
> We always want to have the number of pages (> 0) to the next section
> boundary, starting from the current pfn.
> 
> Suggested-by: Segher Boessenkool <segher@...nel.crashing.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Wei Yang <richardw.yang@...ux.intel.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

LGTM.

Reviewed-by: Baoquan He <bhe@...hat.com>

> ---
>  mm/memory_hotplug.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0a54ffac8c68..c30191183c04 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -528,7 +528,8 @@ void __remove_pages(unsigned long pfn, unsigned long nr_pages,
>  	for (; pfn < end_pfn; pfn += cur_nr_pages) {
>  		cond_resched();
>  		/* Select all remaining pages up to the next section boundary */
> -		cur_nr_pages = min(end_pfn - pfn, -(pfn | PAGE_SECTION_MASK));
> +		cur_nr_pages = min(end_pfn - pfn,
> +				   SECTION_ALIGN_UP(pfn + 1) - pfn);
>  		__remove_section(pfn, cur_nr_pages, map_offset, altmap);
>  		map_offset = 0;
>  	}
> -- 
> 2.24.1
>