When a page is HWPoisoned and later offlined and onlined back, a BUG warning is raised in the kernel: BUG: Bad page state in process mem-on-off-test pfn:7ae3b page:f000000001eb8ec0 count:0 mapcount:0 mapping: (null) index:0x1 flags: 0x3ffff800200000(hwpoison) raw: 003ffff800200000 0000000000000000 0000000000000001 00000000ffffffff raw: 5deadbeef0000100 5deadbeef0000200 0000000000000000 c0000007fe055800 page dumped because: page still charged to cgroup page->mem_cgroup:c0000007fe055800 Modules linked in: pseries_rng rng_core vmx_crypto virtio_balloon ip_tables x_tables autofs4 virtio_blk virtio_net virtio_pci virtio_ring virtio CPU: 34 PID: 5946 Comm: mem-on-off-test Tainted: G B 4.11.0-rc7-hwp #1 Call Trace: [c0000007e4a737f0] [c000000000958e8c] dump_stack+0xb0/0xf0 (unreliable) [c0000007e4a73830] [c00000000021588c] bad_page+0x11c/0x190 [c0000007e4a738c0] [c00000000021757c] free_pcppages_bulk+0x46c/0x600 [c0000007e4a73990] [c00000000021924c] free_hot_cold_page+0x2ec/0x320 [c0000007e4a739e0] [c0000000002a6440] generic_online_page+0x50/0x70 [c0000007e4a73a10] [c0000000002a6184] online_pages_range+0x94/0xe0 [c0000007e4a73a70] [c00000000005a2b0] walk_system_ram_range+0xe0/0x120 [c0000007e4a73ac0] [c0000000002cce44] online_pages+0x2b4/0x6b0 [c0000007e4a73b60] [c000000000600558] memory_subsys_online+0x218/0x270 [c0000007e4a73bf0] [c0000000005dec84] device_online+0xb4/0x110 [c0000007e4a73c30] [c000000000600f00] store_mem_state+0xc0/0x190 [c0000007e4a73c70] [c0000000005da1d4] dev_attr_store+0x34/0x60 [c0000007e4a73c90] [c000000000377c70] sysfs_kf_write+0x60/0xa0 [c0000007e4a73cb0] [c0000000003769fc] kernfs_fop_write+0x16c/0x240 [c0000007e4a73d00] [c0000000002d1b0c] __vfs_write+0x3c/0x1b0 [c0000007e4a73d90] [c0000000002d34dc] vfs_write+0xcc/0x230 [c0000007e4a73de0] [c0000000002d50e0] SyS_write+0x60/0x110 [c0000007e4a73e30] [c00000000000b760] system_call+0x38/0xfc This has been seen on x86 kvm guest, PowerPC bare metal system and KVM guest. The issue is that the onlined page has already the mem_cgroup field set. It seems that the mem_cgroup field should be cleared when the page is poisoned, which is done in the first patch of this series. Then when the page is onlined back, the BUG warning is no more triggered, but the page is now available for use, and once a process is using it, it got killed because of the memory error. It seems that the page should be ignored when onlined, as it is when it is offlined (introduced by commit b023f46813cd "memory-hotplug: skip HWPoisoned page when offlining pages"). The second patch of this series is skipping HWPoisoned page when the memory block is onlined back. To be honest, I don't feel so comfortable with this series. It seems to fix the issue, but I'm not sure this is the right way to achieve that. Please advise. Laurent Dufour (2): mm: Uncharge poisoned pages mm: skip HWPoisoned pages when onlining pages mm/memory-failure.c | 1 + mm/memory_hotplug.c | 2 ++ 2 files changed, 3 insertions(+) -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
