From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id E68FE8D003A for ; Thu, 20 Jan 2011 13:49:18 -0500 (EST) Date: Thu, 20 Jan 2011 12:49:15 -0600 (CST) From: Christoph Lameter Subject: Re: [PATCH 1/3] When migrate_pages returns 0, all pages must have been released In-Reply-To: <20110120182444.GA9506@random.random> Message-ID: References: <20110120182444.GA9506@random.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Minchan Kim , Andrew Morton , linux-mm , LKML , Mel Gorman List-ID: On Thu, 20 Jan 2011, Andrea Arcangeli wrote: > Hello, > > On Thu, Jan 20, 2011 at 11:30:35AM -0600, Christoph Lameter wrote: > > On Fri, 21 Jan 2011, Minchan Kim wrote: > > > > > diff --git a/mm/migrate.c b/mm/migrate.c > > > index 46fe8cc..7d34237 100644 > > > --- a/mm/migrate.c > > > +++ b/mm/migrate.c > > > @@ -772,6 +772,7 @@ uncharge: > > > unlock: > > > unlock_page(page); > > > > > > +move_newpage: > > > if (rc != -EAGAIN) { > > > /* > > > * A page that has been migrated has all references > > > @@ -785,8 +786,6 @@ unlock: > > > putback_lru_page(page); > > > } > > > > > > -move_newpage: > > > - > > > /* > > > * Move the new page to the LRU. If migration was not successful > > > * then this will free the page. > > > > > > > What does this do? Not covered by the description. > > It makes a difference for the two goto move_newpage, when rc = > 0. Otherwise the function will return 0, despite > putback_lru_page(page) wasn't called (and the caller of migrate_pages > won't call putback_lru_pages if migrate_pages returned 0). Think about the difference: Moving the move_newpage will now cause another removal and freeing of the page if rc != -EAGAIN. The first goto move_newpage (because page count is 1) will now mean that the page is freed twice. One because of the rc != EAGAIN branch and then another time by the following putback_lru_page(). -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org