[PATCH 5.5 057/367] mm/migrate.c: also overwrite error when it is bigger than zero

[Greg Kroah-Hartman]

From: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>

commit dfe9aa23cab7880a794db9eb2d176c00ed064eb6 upstream.

If we get here after successfully adding page to list, err would be 1 to
indicate the page is queued in the list.

Current code has two problems:

  * on success, 0 is not returned
  * on error, if add_page_for_migratioin() return 1, and the following err1
    from do_move_pages_to_node() is set, the err1 is not returned since err
    is 1

And these behaviors break the user interface.

Link: http://lkml.kernel.org/r/20200119065753.21694-1-richardw.yang@xxxxxxxxxxxxxxx
Fixes: 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@xxxxxxxxxxxxxxx>
Acked-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1676,7 +1676,7 @@ out_flush:
 	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;