From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id E38766B01AE for ; Tue, 23 Mar 2010 13:24:15 -0400 (EDT) Date: Tue, 23 Mar 2010 12:22:57 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages In-Reply-To: <1269347146-7461-3-git-send-email-mel@csn.ul.ie> Message-ID: References: <1269347146-7461-1-git-send-email-mel@csn.ul.ie> <1269347146-7461-3-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 23 Mar 2010, Mel Gorman wrote: > diff --git a/mm/migrate.c b/mm/migrate.c > index 98eaaf2..6eb1efe 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -603,6 +603,19 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, > */ > if (PageAnon(page)) { > rcu_read_lock(); > + > + /* > + * If the page has no mappings any more, just bail. An > + * unmapped anon page is likely to be freed soon but worse, > + * it's possible its anon_vma disappeared between when > + * the page was isolated and when we reached here while > + * the RCU lock was not held > + */ > + if (!page_mapcount(page)) { > + rcu_read_unlock(); > + goto uncharge; > + } > + > rcu_locked = 1; > anon_vma = page_anon_vma(page); > atomic_inc(&anon_vma->migrate_refcount); A way to make this simpler would be to move "rcu_locked = 1" before the if statement and then do if (!page_mapcount(page)) goto rcu_unlock; -- 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