Re: Zram writeback feature unstable with heavy swap utilization - BUG: Bad page state in process...

[Minchan Kim]

On Fri, Jul 27, 2018 at 01:00:01PM +0200, Tino Lehnig wrote:
> On 07/27/2018 11:14 AM, Minchan Kim wrote:
> > I tried to reproduce with KVM but was not successful and I don't have
> > real mahcine to reproduce it. I am asking one device for it.
> > 
> > Anyway, I want to try this patch.
> > Could you apply attached two patches?
> 
> Thanks, I applied the patches on 4.18-rc6, but unfortunately, they do not
> solve the problem for me. Kernel message below.

Thanks for the testing.

> 
> > I am confusing. You mean after 4.15-rc9, you are not seeing*hung*  problem?
> 
> Correct.
> 
> > So you mean you see page state bug with recent kernel right?
> > It seems there are two problems now.
> > 
> > 1. Hung and 2. bad page
> > 
> > What bugs between them happens against what kernel version?
> > Could you clarify it?
> 
> * pre 0bcac06f27d75 (4.15-rc1): all good
> * 4.15-rc1: hung task (I have not encountered bad page here yet...)
> * 4.15-rc2 through 4.15-rc8: hung task + bad page (very rare)
> * 4.15-rc9 and newer: bad page

And bad page is always with writeback enable?

writeback enable means "echo "some dev" > /sys/block/zram0/backing_dev,
not just enable CONFIG_ZRAM_WRITEBACK.

> --
> 
> [  809.149272] BUG: Bad page state in process kvm  pfn:1cb08a8
> [  809.149332] flags: 0x57ffffc0000008(uptodate)
> [  809.149350] raw: 0057ffffc0000008 dead000000000100 dead000000000200
> 0000000000000000
> [  809.149378] raw: 0000000000000001 0000000000000000 00000000ffffffff
> 0000000000000000
> [  809.149405] page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag set
> [  809.149427] bad because of flags: 0x8(uptodate)
> [  809.149444] Modules linked in: lz4 lz4_compress zram
> [  809.149450] CPU: 14 PID: 3734 Comm: kvm Not tainted 4.18.0-rc6+ #1
> [  809.149450] Hardware name: Supermicro Super Server/X10DRL-i, BIOS 3.0a
> 02/09/2018
> [  809.149451] Call Trace:
> [  809.149458]  dump_stack+0x63/0x85
> [  809.149463]  bad_page+0xc1/0x120
> [  809.149465]  check_new_page_bad+0x67/0x80
> [  809.149467]  get_page_from_freelist+0xe25/0x12f0
> [  809.149469]  __alloc_pages_nodemask+0xfd/0x280
> [  809.149472]  alloc_pages_vma+0x88/0x1c0
> [  809.149475]  do_swap_page+0x346/0x910
> [  809.149477]  __handle_mm_fault+0x815/0x1170
> [  809.149479]  handle_mm_fault+0x102/0x200
> [  809.149481]  __get_user_pages+0x131/0x680
> [  809.149483]  get_user_pages_unlocked+0x145/0x1e0
> [  809.149488]  __gfn_to_pfn_memslot+0x10b/0x3c0
> [  809.149491]  try_async_pf+0x86/0x230
> [  809.149494]  tdp_page_fault+0x12d/0x290
> [  809.149496]  kvm_mmu_page_fault+0x74/0x5d0
> [  809.149499]  ? call_function_interrupt+0xa/0x20
> [  809.149502]  ? vmexit_fill_RSB+0x10/0x40
> [  809.149503]  ? vmexit_fill_RSB+0x1c/0x40
> [  809.149504]  ? vmexit_fill_RSB+0x10/0x40
> [  809.149505]  ? vmexit_fill_RSB+0x1c/0x40
> [  809.149506]  ? vmexit_fill_RSB+0x10/0x40
> [  809.149507]  ? vmexit_fill_RSB+0x1c/0x40
> [  809.149508]  ? vmexit_fill_RSB+0x10/0x40
> [  809.149509]  ? vmexit_fill_RSB+0x1c/0x40
> [  809.149510]  ? vmexit_fill_RSB+0x10/0x40
> [  809.149513]  handle_ept_violation+0xdf/0x1a0
> [  809.149514]  vmx_handle_exit+0xa5/0x11c0
> [  809.149516]  ? vmx_vcpu_run+0x3bb/0x620
> [  809.149519]  kvm_arch_vcpu_ioctl_run+0x9b3/0x1980
> [  809.149522]  kvm_vcpu_ioctl+0x3a0/0x5e0
> [  809.149523]  ? kvm_vcpu_ioctl+0x3a0/0x5e0
> [  809.149526]  do_vfs_ioctl+0xa6/0x620
> [  809.149527]  ksys_ioctl+0x75/0x80
> [  809.149529]  __x64_sys_ioctl+0x1a/0x20
> [  809.149532]  do_syscall_64+0x5a/0x110
> [  809.149534]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  809.149536] RIP: 0033:0x7fd3c5572dd7
> [  809.149536] Code: 00 00 00 48 8b 05 c1 80 2b 00 64 c7 00 26 00 00 00 48
> c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48>
> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 91 80 2b 00 f7 d8 64 89 01 48
> [  809.149563] RSP: 002b:00007fd3b07fc538 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
> [  809.149565] RAX: ffffffffffffffda RBX: 000000000000ae80 RCX:
> 00007fd3c5572dd7
> [  809.149566] RDX: 0000000000000000 RSI: 000000000000ae80 RDI:
> 0000000000000014
> [  809.149566] RBP: 00007fd3b9b13000 R08: 0000558cb94bb350 R09:
> 00000000ffffffff
> [  809.149567] R10: 0005577fd3b06fe6 R11: 0000000000000246 R12:
> 0000000000000000
> [  809.149568] R13: 00007fd3ba146000 R14: 0000000000000000 R15:
> 00007fd3b9b13000
> [  809.149570] Disabling lock debugging due to kernel taint
> 
> -- 
> Kind regards,
> 
> Tino Lehnig