Re: [PATCH] mm/migrate.c: also overwrite error when it is bigger than zero

[Wei Yang <richardw.yang@linux.intel.com>]

On Fri, Jan 17, 2020 at 03:45:34PM +0800, Wei Yang wrote:
>If we get here after successfully adding page to list, err would be
>the number of pages in the list.
>
>Current code has two problems:
>
>  * on success, 0 is not returned
>  * on error, the real error code is not returned
>

Well, this breaks the user interface. User would receive 1 even the migration
succeed.

The change is introduced by e0153fc2c760 ("mm: move_pages: return valid node
id in status if the page is already on the target node").

>Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>---
> mm/migrate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/mm/migrate.c b/mm/migrate.c
>index 557da996b936..c3ef70de5876 100644
>--- a/mm/migrate.c
>+++ b/mm/migrate.c
>@@ -1677,7 +1677,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> 	err1 = do_move_pages_to_node(mm, &pagelist, current_node);
> 	if (!err1)
> 		err1 = store_status(status, start, current_node, i - start);
>-	if (!err)
>+	if (err >= 0)
> 		err = err1;
> out:
> 	return err;
>-- 
>2.17.1

-- 
Wei Yang
Help you, Help me