stripe_index's value was set again in latter line:
stripe_index = 0;
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
 
                        /* push stripe_nr back to the start of the full stripe */
                        stripe_nr = raid56_full_stripe_start;
-                       do_div(stripe_nr, stripe_len);
-
-                       stripe_index = do_div(stripe_nr, nr_data_stripes(map));
+                       do_div(stripe_nr, stripe_len * nr_data_stripes(map));
 
                        /* RAID[56] write or recovery. Return all stripes */
                        num_stripes = map->num_stripes;