From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH] virtio-balloon: fix managed page counts when migrating pages between zones Date: Thu, 5 Dec 2019 10:04:22 +0100 Message-ID: References: <20191204204807.8025-1-david@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20191204204807.8025-1-david@redhat.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: linux-kernel@vger.kernel.org Cc: Yumei Huang , "Michael S. Tsirkin" , stable@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Andrew Morton , Jiang Liu List-Id: virtualization@lists.linuxfoundation.org On 04.12.19 21:48, David Hildenbrand wrote: > In case we have to migrate a ballon page to a newpage of another zone, the > managed page count of both zones is wrong. Paired with memory offlining > (which will adjust the managed page count), we can trigger kernel crashes > and all kinds of different symptoms. > > One way to reproduce: > 1. Start a QEMU guest with 4GB, no NUMA > 2. Hotplug a 1GB DIMM and only the memory to ZONE_NORMAL > 3. Inflate the balloon to 1GB > 4. Unplug the DIMM (be quick, otherwise unmovable data ends up on it) > 5. Observe /proc/zoneinfo > Node 0, zone Normal > pages free 16810 > min 24848885473806 > low 18471592959183339 > high 36918337032892872 > spanned 262144 > present 262144 > managed 18446744073709533486 > 6. Do anything that requires some memory (e.g., inflate the balloon some > more). The OOM goes crazy and the system crashes > [ 238.324946] Out of memory: Killed process 537 (login) total-vm:27584kB, anon-rss:860kB, file-rss:0kB, shmem-rss:00 > [ 238.338585] systemd invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE), order=0, oom_score_adj=0 > [ 238.339420] CPU: 0 PID: 1 Comm: systemd Tainted: G D W 5.4.0-next-20191204+ #75 > [ 238.340139] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4 > [ 238.341121] Call Trace: > [ 238.341337] dump_stack+0x8f/0xd0 > [ 238.341630] dump_header+0x61/0x5ea > [ 238.341942] oom_kill_process.cold+0xb/0x10 > [ 238.342299] out_of_memory+0x24d/0x5a0 > [ 238.342625] __alloc_pages_slowpath+0xd12/0x1020 > [ 238.343024] __alloc_pages_nodemask+0x391/0x410 > [ 238.343407] pagecache_get_page+0xc3/0x3a0 > [ 238.343757] filemap_fault+0x804/0xc30 > [ 238.344083] ? ext4_filemap_fault+0x28/0x42 > [ 238.344444] ext4_filemap_fault+0x30/0x42 > [ 238.344789] __do_fault+0x37/0x1a0 > [ 238.345087] __handle_mm_fault+0x104d/0x1ab0 > [ 238.345450] handle_mm_fault+0x169/0x360 > [ 238.345790] do_user_addr_fault+0x20d/0x490 > [ 238.346154] do_page_fault+0x31/0x210 > [ 238.346468] async_page_fault+0x43/0x50 > [ 238.346797] RIP: 0033:0x7f47eba4197e > [ 238.347110] Code: Bad RIP value. > [ 238.347387] RSP: 002b:00007ffd7c0c1890 EFLAGS: 00010293 > [ 238.347834] RAX: 0000000000000002 RBX: 000055d196a20a20 RCX: 00007f47eba4197e > [ 238.348437] RDX: 0000000000000033 RSI: 00007ffd7c0c18c0 RDI: 0000000000000004 > [ 238.349047] RBP: 00007ffd7c0c1c20 R08: 0000000000000000 R09: 0000000000000033 > [ 238.349660] R10: 00000000ffffffff R11: 0000000000000293 R12: 0000000000000001 > [ 238.350261] R13: ffffffffffffffff R14: 0000000000000000 R15: 00007ffd7c0c18c0 > [ 238.350878] Mem-Info: > [ 238.351085] active_anon:3121 inactive_anon:51 isolated_anon:0 > [ 238.351085] active_file:12 inactive_file:7 isolated_file:0 > [ 238.351085] unevictable:0 dirty:0 writeback:0 unstable:0 > [ 238.351085] slab_reclaimable:5565 slab_unreclaimable:10170 > [ 238.351085] mapped:3 shmem:111 pagetables:155 bounce:0 > [ 238.351085] free:720717 free_pcp:2 free_cma:0 > [ 238.353757] Node 0 active_anon:12484kB inactive_anon:204kB active_file:48kB inactive_file:28kB unevictable:0kB iss > [ 238.355979] Node 0 DMA free:11556kB min:36kB low:48kB high:60kB reserved_highatomic:0KB active_anon:152kB inactivB > [ 238.358345] lowmem_reserve[]: 0 2955 2884 2884 2884 > [ 238.358761] Node 0 DMA32 free:2677864kB min:7004kB low:10028kB high:13052kB reserved_highatomic:0KB active_anon:0B > [ 238.361202] lowmem_reserve[]: 0 0 72057594037927865 72057594037927865 72057594037927865 > [ 238.361888] Node 0 Normal free:193448kB min:99395541895224kB low:73886371836733356kB high:147673348131571488kB reB > [ 238.364765] lowmem_reserve[]: 0 0 0 0 0 > [ 238.365101] Node 0 DMA: 7*4kB (U) 5*8kB (UE) 6*16kB (UME) 2*32kB (UM) 1*64kB (U) 2*128kB (UE) 3*256kB (UME) 2*512B > [ 238.366379] Node 0 DMA32: 0*4kB 1*8kB (U) 2*16kB (UM) 2*32kB (UM) 2*64kB (UM) 1*128kB (U) 1*256kB (U) 1*512kB (U)B > [ 238.367654] Node 0 Normal: 1985*4kB (UME) 1321*8kB (UME) 844*16kB (UME) 524*32kB (UME) 300*64kB (UME) 138*128kB (B > [ 238.369184] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB > [ 238.369915] 130 total pagecache pages > [ 238.370241] 0 pages in swap cache > [ 238.370533] Swap cache stats: add 0, delete 0, find 0/0 > [ 238.370981] Free swap = 0kB > [ 238.371239] Total swap = 0kB > [ 238.371488] 1048445 pages RAM > [ 238.371756] 0 pages HighMem/MovableOnly > [ 238.372090] 306992 pages reserved > [ 238.372376] 0 pages cma reserved > [ 238.372661] 0 pages hwpoisoned > > In another instance (older kernel), I was able to observe this > (negative page count :/): > [ 180.896971] Offlined Pages 32768 > [ 182.667462] Offlined Pages 32768 > [ 184.408117] Offlined Pages 32768 > [ 186.026321] Offlined Pages 32768 > [ 187.684861] Offlined Pages 32768 > [ 189.227013] Offlined Pages 32768 > [ 190.830303] Offlined Pages 32768 > [ 190.833071] Built 1 zonelists, mobility grouping on. Total pages: -36920272750453009 > > In another instance (older kernel), I was no longer able to start any > process: > [root@vm ~]# [ 214.348068] Offlined Pages 32768 > [ 215.973009] Offlined Pages 32768 > cat /proc/meminfo > -bash: fork: Cannot allocate memory > [root@vm ~]# cat /proc/meminfo > -bash: fork: Cannot allocate memory > > Fix it by properly adjusting the managed page count when migrating. The > managed page count of the zones now looks after unplug of the DIMM > (and after deflating the balloon) just like before inflating the balloon > (and plugging+onlining the DIMM). > > Reported-by: Yumei Huang > Fixes: 3dcc0571cd64 ("mm: correctly update zone->managed_pages") > Cc: # v3.11+ > Cc: "Michael S. Tsirkin" > Cc: Jason Wang > Cc: Jiang Liu > Cc: Andrew Morton > Cc: virtualization@lists.linux-foundation.org > Signed-off-by: David Hildenbrand > --- > drivers/virtio/virtio_balloon.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 15b7f1d8c334..1089b07679cf 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -742,6 +742,12 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, > > mutex_unlock(&vb->balloon_lock); > > + /* fixup the managed page count (esp. of the zone) */ > + if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { > + adjust_managed_page_count(page, 1); > + adjust_managed_page_count(newpage, -1); > + } > + > put_page(page); /* balloon reference */ > > return MIGRATEPAGE_SUCCESS; > I'll resend, adjusting the count while we are still guaranteed to hold a reference to newpage (after it was enqueued, it could get dequeued and freed). -- Thanks, David / dhildenb