Re: [PATCH v3 2/6] mm/migrate: correct failure handling if !hugepage_migration_support()

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

On Fri, Dec 13, 2013 at 03:53:27PM +0900, Joonsoo Kim wrote:
> We should remove the page from the list if we fail with ENOSYS,
> since migrate_pages() consider error cases except -ENOMEM and -EAGAIN
> as permanent failure and it assumes that the page would be removed from
> the list. Without this patch, we could overcount number of failure.
> 
> In addition, we should put back the new hugepage if
> !hugepage_migration_support(). If not, we would leak hugepage memory.
> 
> Acked-by: Christoph Lameter <cl@linux.com>
> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

Thanks,
Naoya Horiguchi

> diff --git a/mm/migrate.c b/mm/migrate.c
> index c6ac87a..b1cfd01 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1011,7 +1011,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  {
>  	int rc = 0;
>  	int *result = NULL;
> -	struct page *new_hpage = get_new_page(hpage, private, &result);
> +	struct page *new_hpage;
>  	struct anon_vma *anon_vma = NULL;
>  
>  	/*
> @@ -1021,9 +1021,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  	 * tables or check whether the hugepage is pmd-based or not before
>  	 * kicking migration.
>  	 */
> -	if (!hugepage_migration_support(page_hstate(hpage)))
> +	if (!hugepage_migration_support(page_hstate(hpage))) {
> +		putback_active_hugepage(hpage);
>  		return -ENOSYS;
> +	}
>  
> +	new_hpage = get_new_page(hpage, private, &result);
>  	if (!new_hpage)
>  		return -ENOMEM;
>  
> -- 
> 1.7.9.5
> 

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