linux-kernel - Re: [PATCH v1 07/11] mm/page_isolation: simplify return value of start_isolate_page

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Date:   Wed, 19 Aug 2020 15:00:14 +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 07/11] mm/page_isolation: simplify return value of
 start_isolate_page_range()

On Wed 19-08-20 12:11:53, David Hildenbrand wrote:
> Callers no longer need the number of isolated pageblocks. Let's
> simplify.
> 
> 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 | 2 +-
>  mm/page_alloc.c     | 2 +-
>  mm/page_isolation.c | 7 ++-----
>  3 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 098361fcb4504..0011a1115381c 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1503,7 +1503,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  	ret = start_isolate_page_range(start_pfn, end_pfn,
>  				       MIGRATE_MOVABLE,
>  				       MEMORY_OFFLINE | REPORT_FAILURE);
> -	if (ret < 0) {
> +	if (ret) {
>  		reason = "failure to isolate range";
>  		goto failed_removal;
>  	}
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 03f585f95dc60..848664352dfe2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8456,7 +8456,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>  
>  	ret = start_isolate_page_range(pfn_max_align_down(start),
>  				       pfn_max_align_up(end), migratetype, 0);
> -	if (ret < 0)
> +	if (ret)
>  		return ret;
>  
>  	/*
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 242c03121d731..b066c860e606e 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -170,8 +170,7 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
>   * pageblocks we may have modified and return -EBUSY to caller. This
>   * prevents two threads from simultaneously working on overlapping ranges.
>   *
> - * Return: the number of isolated pageblocks on success and -EBUSY if any part
> - * of range cannot be isolated.
> + * Return: 0 on success and -EBUSY if any part of range cannot be isolated.
>   */
>  int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  			     unsigned migratetype, int flags)
> @@ -179,7 +178,6 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  	unsigned long pfn;
>  	unsigned long undo_pfn;
>  	struct page *page;
> -	int nr_isolate_pageblock = 0;
>  
>  	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
>  	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
> @@ -193,10 +191,9 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  				undo_pfn = pfn;
>  				goto undo;
>  			}
> -			nr_isolate_pageblock++;
>  		}
>  	}
> -	return nr_isolate_pageblock;
> +	return 0;
>  undo:
>  	for (pfn = start_pfn;
>  	     pfn < undo_pfn;
> -- 
> 2.26.2

-- 
Michal Hocko
SUSE Labs