From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: mmotm 2015-01-22-15-04: qemu failure due to 'mm: memcontrol: remove unnecessary soft limit tree node test' Date: Fri, 23 Jan 2015 07:46:43 -0800 Message-ID: <54C26CE3.2060001@roeck-us.net> References: <54c1822d.RtdGfWPekQVAw8Ly%akpm@linux-foundation.org> <20150123050802.GB22751@roeck-us.net> <20150123141817.GA22926@phnom.home.cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: akpm@linux-foundation.org, mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-next@vger.kernel.org, sfr@canb.auug.org.au, mhocko@suse.cz, cl@linux.com To: Johannes Weiner Return-path: In-Reply-To: <20150123141817.GA22926@phnom.home.cmpxchg.org> Sender: linux-next-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 01/23/2015 06:18 AM, Johannes Weiner wrote: > Hi Guenter, > > CC'ing Christoph for slub-stuff: > > On Thu, Jan 22, 2015 at 09:08:02PM -0800, Guenter Roeck wrote: >> On Thu, Jan 22, 2015 at 03:05:17PM -0800, akpm@linux-foundation.org wrote: >>> The mm-of-the-moment snapshot 2015-01-22-15-04 has been uploaded to >>> >>> http://www.ozlabs.org/~akpm/mmotm/ >>> >> qemu test for ppc64 fails with >> >> Unable to handle kernel paging request for data at address 0x0000af50 >> Faulting instruction address: 0xc00000000089d5d4 >> Oops: Kernel access of bad area, sig: 11 [#1] >> >> with the following call stack: >> >> Call Trace: >> [c00000003d32f920] [c00000000089d588] .__slab_alloc.isra.44+0x7c/0x6f4 >> (unreliable) >> [c00000003d32fa90] [c00000000020cf8c] .kmem_cache_alloc_node_trace+0x12c/0x3b0 >> [c00000003d32fb60] [c000000000bceeb4] .mem_cgroup_init+0x128/0x1b0 >> [c00000003d32fbf0] [c00000000000a2b4] .do_one_initcall+0xd4/0x260 >> [c00000003d32fce0] [c000000000ba26a8] .kernel_init_freeable+0x244/0x32c >> [c00000003d32fdb0] [c00000000000ac24] .kernel_init+0x24/0x140 >> [c00000003d32fe30] [c000000000009564] .ret_from_kernel_thread+0x58/0x74 >> >> bisect log: > > [...] > >> # first bad commit: [a40d0d2cf21e2714e9a6c842085148c938bf36ab] mm: memcontrol: remove unnecessary soft limit tree node test > > The change in question is this: > > mm: memcontrol: remove unnecessary soft limit tree node test > > kzalloc_node() automatically falls back to nodes with suitable memory. > > Signed-off-by: Johannes Weiner > Acked-by: Michal Hocko > Reviewed-by: Vladimir Davydov > Signed-off-by: Andrew Morton > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fb9788af4a3e..10db4a654d68 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4539,13 +4539,10 @@ static void __init mem_cgroup_soft_limit_tree_init(void) > { > struct mem_cgroup_tree_per_node *rtpn; > struct mem_cgroup_tree_per_zone *rtpz; > - int tmp, node, zone; > + int node, zone; > > for_each_node(node) { > - tmp = node; > - if (!node_state(node, N_NORMAL_MEMORY)) > - tmp = -1; > - rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp); > + rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node); > BUG_ON(!rtpn); > > soft_limit_tree.rb_tree_per_node[node] = rtpn; > > -- > > Is the assumption of this patch wrong? Does the specified node have > to be online for the fallback to work? > I added some debugging. First, the problem is only seen with SMP disabled. Second, there is only one online node. Without your patch: Node 0 online 1 high 1 memory 1 cpu 0 normal 1 tmp 0 rtpn c00000003d240600 Node 1 online 0 high 0 memory 0 cpu 0 normal 0 tmp -1 rtpn c00000003d240640 Node 2 online 0 high 0 memory 0 cpu 0 normal 0 tmp -1 rtpn c00000003d240680 [ and so on up to node 255 ] With your patch: Node 0 online 1 high 1 memory 1 cpu 0 normal 1 rtpn c00000003d240600 Unable to handle kernel paging request for data at address 0x0000af50 Faulting instruction address: 0xc000000000895a3c Oops: Kernel access of bad area, sig: 11 [#1] The log message is after the call to kzalloc_node. So it doesn't look like the fallback is working, at least not with ppc64 in non-SMP mode. Guenter