On Mon, Dec 09, 2013 at 04:40:06PM +0000, Christoph Lameter wrote: > On Mon, 9 Dec 2013, Joonsoo Kim wrote: > > > First, we don't use error number in fail case. Call-path related to > > new_page_node() is shown in the following. > > > > do_move_page_to_node_array() -> migrate_pages() -> unmap_and_move() > > -> new_page_node() > > > > If unmap_and_move() failed, migrate_pages() also returns err, and then > > do_move_page_to_node_array() skips to set page's status to user buffer. > > So we don't need to set error number to each pages on failure case. > > I dont get this. new_page_node() sets the error condition in the > page_to_node array before this patch. There is no post processing in > do_move_page_to_node_array(). The function simply returns and relies on > new_page_node() to have set the page status. do_move_pages() then returns > the page status back to userspace. How does the change preserve these > diagnostics? Hello, Christoph. In do_move_pages(), if error occurs, 'goto out_pm' is executed and the page status doesn't back to userspace. So we don't need to store err number. Perhaps my description should be changed something like below. *do_move_pages()* -> do_move_page_to_node_array() -> migrate_pages() -> unmap_and_move() -> new_page_node() If unmap_and_move() failed, migrate_pages() also returns err, and then *do_move_pages()* skips to set page's status to user buffer. So we don't need to set error number to each pages on failure case. Is it sufficient explanation? > > > Next, we don't need to set node id of the new page in unmap_and_move(), > > since it cannot be different with pm->node. In new_page_node(), we always > > try to allocate the page in exact node by referencing pm->node. So it is > > sufficient to set node id of the new page in new_page_node(), instead of > > unmap_and_move(). > > Thats a good thought. Thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>