3.11.0-rc1: kernel BUG at mm/migrate.c:458 in page migration

[Naoya Horiguchi]

Hi,

v3.11-rc1 kernel triggers VM_BUG_ON(PageUnevictable(page)) in migrate_page_copy
when I do page migration like the following:

  $ sleep 100 &
  $ migratepages $(pgrep sleep) 0 1

  kernel BUG at /src/linux-dev/mm/migrate.c:458!
  invalid opcode: 0000 [#1] SMP
  Modules linked in: ebtable_nat ebtables xt_CHECKSUM iptable_mangle bridge lockd stp llc sunrpc bnep bluetooth rfkill ip6t_REJECT be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i nf_conntrack_ipv4 nf_conntrack_ipv6 cxgb3 mdio nf_defrag_ipv4 libcxgbi nf_defrag_ipv6 xt_state ib_iser nf_conntrack ip6table_filter ip6_tables rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi igb ptp pps_core ioatdma iTCO_wdt iTCO_vendor_support i2c_algo_bit dca pcspkr i7core_edac edac_core lpc_ich mfd_core i2c_i801 i2c_core acpi_power_meter microcode uinput
  CPU: 0 PID: 1443 Comm: migratepages Tainted: G        W    3.11.0-rc1-00009-g3ffee0e #84
  Hardware name: NEC NEC Express5800/R120b-1 [N8100-1719F]/MS-91E7-001, BIOS 4.6.3C19 02/10/2011
  task: ffff88042566c3e0 ti: ffff88041e760000 task.ti: ffff88041e760000
  RIP: 0010:[<ffffffff8118e7e5>]  [<ffffffff8118e7e5>] migrate_page_copy+0x1c5/0x1d0
  RSP: 0018:ffff88041e761ad8  EFLAGS: 00010206
  RAX: 002ffc000012000d RBX: ffffea0008df6100 RCX: 0000000000000000
  RDX: 0000000000000028 RSI: ffff880237d85000 RDI: ffff88041a6be000
  RBP: ffff88041e761af8 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: ffffffffffffffc8 R12: ffffea001069af40
  R13: ffff88041e760000 R14: ffffea0008df6100 R15: 0000000000000001
  FS:  00007f166e39b740(0000) GS:ffff880237c00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 000000000209f8e0 CR3: 000000021dd3e000 CR4: 00000000000007f0
  Stack:
   ffffea001069af40 ffffea0008df6100 ffffea001069af40 ffffea001069af40
   ffff88041e761b18 ffffffff8118e84b 0000000000000002 ffffea0008df6100
   ffff88041e761b48 ffffffff8118ebd5 ffffea001069af40 ffffea0008df6100
  Call Trace:
   [<ffffffff8118e84b>] migrate_page+0x5b/0x70
   [<ffffffff8118ebd5>] buffer_migrate_page+0x135/0x170
   [<ffffffff8118e8e8>] move_to_new_page+0x88/0x240
   [<ffffffff8118f360>] migrate_pages+0x750/0x7c0
   [<ffffffff8117c7e0>] ? sp_insert+0xc0/0xc0
   [<ffffffff8117efec>] migrate_to_node+0x9c/0xe0
   [<ffffffff8117f2ba>] do_migrate_pages+0x25a/0x2d0
   [<ffffffff8117f65d>] SYSC_migrate_pages+0x32d/0x390
   [<ffffffff8117f3e9>] ? SYSC_migrate_pages+0xb9/0x390
   [<ffffffff8117f6de>] SyS_migrate_pages+0xe/0x10
   [<ffffffff816a6482>] system_call_fastpath+0x16/0x1b
  Code: 6d 1c 01 41 83 6d 1c 01 e9 a0 fe ff ff 66 0f 1f 84 00 00 00 00 00 4c 89 e7 e8 58 30 fb ff e9 f9 fe ff ff 0f 1f 00 e8 5d 52 50 00 <0f> 0b 66 0f 1f 84 00 00 00 00 00 66 66 66 66 90 55 48 89 e5 41
  RIP  [<ffffffff8118e7e5>] migrate_page_copy+0x1c5/0x1d0
   RSP <ffff88041e761ad8>
  ---[ end trace 3efe05138cc2e0bb ]---

I think that the behavior of PageUnevictable was changed by commit 13f7f78981e4
"mm: pagevec: defer deciding which LRU to add a page to until pagevec drain time"
, and we don't need the VM_BUG_ON any more.
But I'm not sure whether we need more conclusive fix.

Do you have any comments?

Thanks,
Naoya Horiguchi
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