From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx144.postini.com [74.125.245.144]) by kanga.kvack.org (Postfix) with SMTP id 0FFF76B0074 for ; Tue, 8 Jan 2013 23:23:59 -0500 (EST) Received: by mail-pb0-f44.google.com with SMTP id uo1so678787pbc.31 for ; Tue, 08 Jan 2013 20:23:59 -0800 (PST) Date: Tue, 8 Jan 2013 20:23:46 -0800 (PST) From: Hugh Dickins Subject: Re: oops in copy_page_rep() In-Reply-To: <20130108173747.GF9163@redhat.com> Message-ID: References: <20130105152208.GA3386@redhat.com> <20130108163141.GA27555@shutemov.name> <20130108173747.GF9163@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Linus Torvalds , "Kirill A. Shutemov" , Hillf Danton , Dave Jones , Linux Kernel , Andrew Morton , Mel Gorman , Linux-MM , Rik van Riel On Tue, 8 Jan 2013, Andrea Arcangeli wrote: > > Looking at this, one thing that isn't clear is where the page_count is > checked in migrate_misplaced_transhuge_page. Ok that it's unable to > migrate anon transhuge COW shared pages so it doesn't need to mess > with rmap (the mapcount check makes it safe), but it shouldn't be > allowed to migrate memory that has gup direct-IO in flight (and that > can only be detected with a page_count vs mapcount check). Real > migrate does page_freeze_refs to be safe. Mel comments? Yes, I protested to Mel about that before the holidays, and he quickly provided a patch, now in akpm's tree; but checking it again today, I believe it's still not quite right yet - see other mail. Hugh -- 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