Re: [PATCH v2 4/6] mm/page_isolation: cleanup set_migratetype_isolate()

[Vlastimil Babka <vbabka@suse.cz>]

On 7/30/20 11:34 AM, David Hildenbrand wrote:
> Let's clean it up a bit, simplifying error handling and getting rid of
> the label.

Nit: the label was already removed by patch 1/6?

> Reviewed-by: Baoquan He <bhe@redhat.com>
> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  mm/page_isolation.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index d099aac479601..e65fe5d770849 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -17,12 +17,9 @@
>  
>  static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
>  {
> -	struct page *unmovable = NULL;
> -	struct zone *zone;
> +	struct zone *zone = page_zone(page);
> +	struct page *unmovable;
>  	unsigned long flags;
> -	int ret = -EBUSY;
> -
> -	zone = page_zone(page);
>  
>  	spin_lock_irqsave(&zone->lock, flags);
>  
> @@ -51,13 +48,13 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
>  									NULL);
>  
>  		__mod_zone_freepage_state(zone, -nr_pages, mt);
> -		ret = 0;
> +		spin_unlock_irqrestore(&zone->lock, flags);
> +		drain_all_pages(zone);
> +		return 0;
>  	}
>  
>  	spin_unlock_irqrestore(&zone->lock, flags);
> -	if (!ret) {
> -		drain_all_pages(zone);
> -	} else if ((isol_flags & REPORT_FAILURE) && unmovable) {
> +	if (isol_flags & REPORT_FAILURE) {
>  		/*
>  		 * printk() with zone->lock held will likely trigger a
>  		 * lockdep splat, so defer it here.
> @@ -65,7 +62,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
>  		dump_page(unmovable, "unmovable page");
>  	}
>  
> -	return ret;
> +	return -EBUSY;
>  }
>  
>  static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>