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Subject: Re: [Patch v2 3/4] mm/migrate.c: check pagelist in
 move_pages_and_store_status()
To:     Wei Yang <richardw.yang@linux.intel.com>, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@suse.com,
        yang.shi@linux.alibaba.com, rientjes@google.com
References: <20200122011647.13636-1-richardw.yang@linux.intel.com>
 <20200122011647.13636-4-richardw.yang@linux.intel.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <f7f70c42-a9a6-6c84-cdb5-230205703ddf@redhat.com>
Date:   Tue, 28 Jan 2020 11:21:13 +0100
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On 22.01.20 02:16, Wei Yang wrote:
> When pagelist is empty, it is not necessary to do the move and store.
> Also it consolidate the empty list check in one place.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> ---
>  mm/migrate.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index a4d3bd6475e1..80d2bba57265 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1499,9 +1499,6 @@ static int do_move_pages_to_node(struct mm_struct *mm,
>  {
>  	int err;
>  
> -	if (list_empty(pagelist))
> -		return 0;
> -
>  	err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
>  			MIGRATE_SYNC, MR_SYSCALL);
>  	if (err)
> @@ -1589,6 +1586,9 @@ static int move_pages_and_store_status(struct mm_struct *mm, int node,
>  {
>  	int err;
>  
> +	if (list_empty(pagelist))
> +		return 0;
> +
>  	err = do_move_pages_to_node(mm, pagelist, node);
>  	if (err)
>  		return err;
> @@ -1676,9 +1676,6 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>  		current_node = NUMA_NO_NODE;
>  	}
>  out_flush:
> -	if (list_empty(&pagelist))
> -		return err;


Am I wrong or are you discarding an error here? (err could be !0)


-- 
Thanks,

David / dhildenb