From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756605Ab3A0Vkm (ORCPT ); Sun, 27 Jan 2013 16:40:42 -0500 Received: from mail-da0-f53.google.com ([209.85.210.53]:57495 "EHLO mail-da0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756561Ab3A0Vkk (ORCPT ); Sun, 27 Jan 2013 16:40:40 -0500 Date: Sun, 27 Jan 2013 13:40:40 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Shaohua Li cc: Sasha Levin , Andrew Morton , Shaohua Li , Rik van Riel , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: boot warnings due to swap: make each swap partition have one address_space In-Reply-To: <20130127141253.GA27019@kernel.org> Message-ID: References: <5101FFF5.6030503@oracle.com> <20130125042512.GA32017@kernel.org> <20130127141253.GA27019@kernel.org> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 27 Jan 2013, Shaohua Li wrote: > On Sat, Jan 26, 2013 at 06:16:05PM -0800, Hugh Dickins wrote: > > On Fri, 25 Jan 2013, Shaohua Li wrote: > > > On Thu, Jan 24, 2013 at 10:45:57PM -0500, Sasha Levin wrote: > > > > > > Subject: give-each-swapper-space-separate-backing_dev_info > > > > > > The backing_dev_info can't be shared by all swapper address space. > > > > Whyever not? It's perfectly normal for different inodes/address_spaces > > to share a single backing_dev! Sasha's trace says that it's wrong to > > initialize it MAX_SWAPFILES times: fair enough. But why should I now > > want to spend 32kB (not even counting their __percpu counters) on all > > these pseudo-backing_devs? > > That's correct, silly me. Updated it. Looks much more to my taste, thank you! > > > > p.s. a grand little change would be to move page_cluster and swap_setup() > > from mm/swap.c to mm/swap_state.c: they have nothing to do with the other > > contents of swap.c, and everything to do with the contents of swap_state.c. > > Why swap.c is called swap.c is rather a mystery. > > Tried, but looks page_cluster is used in sysctl, moving to swap_state.c will > make it optional. don't want to add another #ifdef, so give up. Good point, thanks for trying, maybe I'll attack it next time it irritates me. I don't yet know whether I approve of your changes or not, but running with them to see (and I'll send another bugfix separately in a moment). I was the one who removed the swap_device_lock() which 2.4 used, because it almost always ended up having to take both swap_list_lock() and swap_device_lock(si). You seem to have done a much better job of separating them usefully, but I need to convince myself that it does end up safely. My reservations so far would be: how many installations actually have more than one swap area, so is it a good tradeoff to add more overhead to help those at the (slight) expense of everyone else? The increasingly ugly page_mapping() worries me, and the static array of swapper_spaces annoys me a little. I'm glad Minchan has now pointed you to Rik's posting of two years ago: I think there are more important changes to be made in that direction. Hugh > > > Subject: init-swap-space-backing-dev-info-once > > > Sasha reported: > Commit "swap: make each swap partition have one address_space" is triggering > a series of warnings on boot: > > [ 3.446071] ------------[ cut here ]------------ > [ 3.446664] WARNING: at lib/debugobjects.c:261 debug_print_object+0x8e/0xb0() > [ 3.447715] ODEBUG: init active (active state 0) object type: percpu_counter hint: (null) > [ 3.450360] Modules linked in: > [ 3.451593] Pid: 1, comm: swapper/0 Tainted: G W 3.8.0-rc4-next-20130124-sasha-00004-g838a1b4 #266 > [ 3.454508] Call Trace: > [ 3.455248] [] warn_slowpath_common+0x8c/0xc0 > [ 3.455248] [] warn_slowpath_fmt+0x41/0x50 > [ 3.455248] [] debug_print_object+0x8e/0xb0 > [ 3.455248] [] __debug_object_init+0x20b/0x290 > [ 3.455248] [] debug_object_init+0x15/0x20 > [ 3.455248] [] __percpu_counter_init+0x6d/0xe0 > [ 3.455248] [] bdi_init+0x1ac/0x270 > [ 3.455248] [] swap_setup+0x3b/0x87 > [ 3.455248] [] ? swap_setup+0x87/0x87 > [ 3.455248] [] kswapd_init+0x11/0x7c > [ 3.455248] [] do_one_initcall+0x8a/0x180 > [ 3.455248] [] do_basic_setup+0x96/0xb4 > [ 3.455248] [] ? loglevel+0x31/0x31 > [ 3.455248] [] ? sched_init_smp+0x150/0x157 > [ 3.455248] [] kernel_init_freeable+0xd2/0x14c > [ 3.455248] [] ? rest_init+0x140/0x140 > [ 3.455248] [] kernel_init+0x9/0xf0 > [ 3.455248] [] ret_from_fork+0x7c/0xb0 > [ 3.455248] [] ? rest_init+0x140/0x140 > [ 3.455248] ---[ end trace 0b176d5c0f21bffb ]--- > > Initialize swap space backing_dev_info once to avoid the warning. > > Reported-by: Sasha Levin > Signed-off-by: Shaohua Li > --- > mm/swap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux/mm/swap.c > =================================================================== > --- linux.orig/mm/swap.c 2013-01-27 21:26:21.942696713 +0800 > +++ linux/mm/swap.c 2013-01-27 21:27:29.233865394 +0800 > @@ -858,8 +858,8 @@ void __init swap_setup(void) > #ifdef CONFIG_SWAP > int i; > > + bdi_init(swapper_spaces[0].backing_dev_info); > for (i = 0; i < MAX_SWAPFILES; i++) { > - bdi_init(swapper_spaces[i].backing_dev_info); > spin_lock_init(&swapper_spaces[i].tree_lock); > INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear); > } >