From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f44.google.com (mail-pb0-f44.google.com [209.85.160.44]) by kanga.kvack.org (Postfix) with ESMTP id 0EF066B0035 for ; Wed, 11 Dec 2013 03:44:25 -0500 (EST) Received: by mail-pb0-f44.google.com with SMTP id rq2so9573458pbb.3 for ; Wed, 11 Dec 2013 00:44:25 -0800 (PST) Received: from LGEMRELSE6Q.lge.com (LGEMRELSE6Q.lge.com. [156.147.1.121]) by mx.google.com with ESMTP id 8si12919370pbe.10.2013.12.11.00.44.23 for ; Wed, 11 Dec 2013 00:44:24 -0800 (PST) Date: Wed, 11 Dec 2013 17:47:19 +0900 From: Joonsoo Kim Subject: Re: [PATCH v2 7/7] mm/migrate: remove result argument on page allocation function for migration Message-ID: <20131211084719.GA2043@lge.com> References: <1386580248-22431-1-git-send-email-iamjoonsoo.kim@lge.com> <1386580248-22431-8-git-send-email-iamjoonsoo.kim@lge.com> <00000142d83adfc7-81b70cc9-c87b-4e7e-bd98-0a97ee21db31-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <00000142d83adfc7-81b70cc9-c87b-4e7e-bd98-0a97ee21db31-000000@email.amazonses.com> Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Andrew Morton , Mel Gorman , Rik van Riel , Rafael Aquini , Naoya Horiguchi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , Zhang Yanfei 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org