Re: [PATCH v2] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm

From: Jia He
Date: Wed May 09 2018 - 21:26:42 EST

Next message: Masami Hiramatsu: "Re: [PATCH] perf buildid-cache: Warn --purge-all failures"
Previous message: Finn Thain: "Re: [PATCH net] macmace: Set platform device coherent_dma_mask"
In reply to: Andrew Morton: "Re: [PATCH v2] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm"
Next in thread: Suzuki K Poulose: "Re: [PATCH v2] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hi Andrew

On 5/10/2018 7:31 AM, Andrew Morton Wrote:

On Fri, 4 May 2018 11:11:46 +0800 Jia He <hejianet@xxxxxxxxx> wrote:

In our armv8a server(QDF2400), I noticed lots of WARN_ON caused by PAGE_SIZE
unaligned for rmap_item->address under memory pressure tests(start 20 guests
and run memhog in the host).

...

In rmap_walk_ksm, the rmap_item->address might still have the STABLE_FLAG,
then the start and end in handle_hva_to_gpa might not be PAGE_SIZE aligned.
Thus it will cause exceptions in handle_hva_to_gpa on arm64.

This patch fixes it by ignoring(not removing) the low bits of address when
doing rmap_walk_ksm.

Signed-off-by: jia.he@xxxxxxxxxxxxxxxx

I assumed you wanted this patch to be committed as
From:jia.he@xxxxxxxxxxxxxxxx rather than From:hejianet@xxxxxxxxx, so I
made that change. Please let me know if this was inappropriate.

Thanks, because there is still some issues in our company's mail server.
I have to use my gmail mailbox.

You can do this yourself by adding an explicit From: line to the very
start of the patch's email text.

Also, a storm of WARN_ONs is pretty poor behaviour. Is that the only
misbehaviour which this bug causes? Do you think the fix should be
backported into earlier kernels?

IMO, it should be backported to stable tree, seems that I missed CC to stable tree ;-)
the stom of WARN_ONs is very easy for me to reproduce.
More than that, I watched a panic (not reproducible) as follows:
[35380.805825] page:ffff7fe003742d80 count:-4871 mapcount:-2126053375 mapping:ÂÂÂÂÂÂÂÂÂ (null) index:0x0
[35380.815024] flags: 0x1fffc00000000000()
[35380.818845] raw: 1fffc00000000000 0000000000000000 0000000000000000 ffffecf981470000
[35380.826569] raw: dead000000000100 dead000000000200 ffff8017c001c000 0000000000000000
[35380.834294] page dumped because: nonzero _refcount
[35380.839069] Modules linked in: vhost_net vhost tap ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter fcoe libfcoe libfc 8021q garp mrp stp llc scsi_transport_fc openvswitch nf_conntrack_ipv6 nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6 nf_nat nf_conntrack vfat fat rpcrdma ib_isert iscsi_target_mod ib_iser libiscsi scsi_transport_iscsi ib_srpt target_core_mod ib_srp scsi_transport_srp ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm ib_cm iw_cm mlx5_ib ib_core crc32_ce ipmi_ssif tpm_tis tpm_tis_core sg nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_multipath ip_tables xfs libcrc32c mlx5_core mlxfw devlink ahci_platform libahci_platform libahci qcom_emac sdhci_acpi sdhci hdma mmc_core hdma_mgmt i2c_qup dm_mirror dm_region_hash dm_log dm_mod
[35380.908341] CPU: 29 PID: 18323 Comm: qemu-kvm Tainted: G WÂÂÂÂÂÂ 4.14.15-5.hxt.aarch64 #1
[35380.917107] Hardware name: <snip for confidential issues>
[35380.930909] Call trace:
[35380.933345] [<ffff000008088f00>] dump_backtrace+0x0/0x22c
[35380.938723] [<ffff000008089150>] show_stack+0x24/0x2c
[35380.943759] [<ffff00000893c078>] dump_stack+0x8c/0xb0
[35380.948794] [<ffff00000820ab50>] bad_page+0xf4/0x154
[35380.953740] [<ffff000008211ce8>] free_pages_check_bad+0x90/0x9c
[35380.959642] [<ffff00000820c430>] free_pcppages_bulk+0x464/0x518
[35380.965545] [<ffff00000820db98>] free_hot_cold_page+0x22c/0x300
[35380.971448] [<ffff0000082176fc>] __put_page+0x54/0x60
[35380.976484] [<ffff0000080b1164>] unmap_stage2_range+0x170/0x2b4
[35380.982385] [<ffff0000080b12d8>] kvm_unmap_hva_handler+0x30/0x40
[35380.988375] [<ffff0000080b0104>] handle_hva_to_gpa+0xb0/0xec
[35380.994016] [<ffff0000080b2644>] kvm_unmap_hva_range+0x5c/0xd0
[35380.999833] [<ffff0000080a8054>] kvm_mmu_notifier_invalidate_range_start+0x60/0xb0
[35381.007387] [<ffff000008271f44>] __mmu_notifier_invalidate_range_start+0x64/0x8c
[35381.014765] [<ffff0000082547c8>] try_to_unmap_one+0x78c/0x7a4
[35381.020493] [<ffff000008276d04>] rmap_walk_ksm+0x124/0x1a0
[35381.025961] [<ffff0000082551b4>] rmap_walk+0x94/0x98
[35381.030909] [<ffff0000082555e4>] try_to_unmap+0x100/0x124
[35381.036293] [<ffff00000828243c>] unmap_and_move+0x480/0x6fc
[35381.041847] [<ffff000008282b6c>] migrate_pages+0x10c/0x288
[35381.047318] [<ffff00000823c164>] compact_zone+0x238/0x954
[35381.052697] [<ffff00000823c944>] compact_zone_order+0xc4/0xe8
[35381.058427] [<ffff00000823d25c>] try_to_compact_pages+0x160/0x294
[35381.064503] [<ffff00000820f074>] __alloc_pages_direct_compact+0x68/0x194
[35381.071187] [<ffff000008210138>] __alloc_pages_nodemask+0xc20/0xf7c
[35381.077437] [<ffff0000082709e4>] alloc_pages_vma+0x1a4/0x1c0
[35381.083080] [<ffff000008285b68>] do_huge_pmd_anonymous_page+0x128/0x324
[35381.089677] [<ffff000008248a24>] __handle_mm_fault+0x71c/0x7e8
[35381.095492] [<ffff000008248be8>] handle_mm_fault+0xf8/0x194
[35381.101049] [<ffff000008240dcc>] __get_user_pages+0x124/0x34c
[35381.106777] [<ffff000008241870>] populate_vma_page_range+0x90/0x9c
[35381.112941] [<ffff000008241940>] __mm_populate+0xc4/0x15c
[35381.118322] [<ffff00000824b294>] SyS_mlockall+0x100/0x164
[35381.123705] Exception stack(0xffff800dce5f3ec0 to 0xffff800dce5f4000)
[35381.130128] 3ec0: 0000000000000003 d6e6024cc9b87e00 0000aaaabe94f000 0000000000000000
[35381.137940] 3ee0: 0000000000000002 0000000000000000 0000000000000000 0000aaaacf6fc3c0
[35381.145753] 3f00: 00000000000000e6 0000aaaacf6fc490 0000ffffeeeab0f0 d6e6024cc9b87e00
[35381.153565] 3f20: 0000000000000000 0000aaaabe81b3c0 0000000000000020 00009e53eff806b5
[35381.161379] 3f40: 0000aaaabe94de48 0000ffffa7c269b0 0000000000000011 0000ffffeeeabf68
[35381.169190] 3f60: 0000aaaaceacfe60 0000aaaabe94f000 0000aaaabe9ba358 0000aaaabe7ffb80
[35381.177003] 3f80: 0000aaaabe9ba000 0000aaaabe959f64 0000000000000000 0000aaaabe94f000
[35381.184815] 3fa0: 0000000000000000 0000ffffeeeabdb0 0000aaaabe5f3bf8 0000ffffeeeabdb0
[35381.192628] 3fc0: 0000ffffa7c269b8 0000000060000000 0000000000000003 00000000000000e6
[35381.200440] 3fe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[35381.208254] [<ffff00000808339c>] __sys_trace_return+0x0/0x4
[35381.213809] Disabling lock debugging due to kernel taint

I ever injected a fault on purpose in kvm_unmap_hva_range by set size=size-0x200, the call trace is similar
as above. Thus, I thought the panic is similarly caused by the root cause of WARN_ON

--
Cheers,
Jia

Next message: Masami Hiramatsu: "Re: [PATCH] perf buildid-cache: Warn --purge-all failures"
Previous message: Finn Thain: "Re: [PATCH net] macmace: Set platform device coherent_dma_mask"
In reply to: Andrew Morton: "Re: [PATCH v2] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm"
Next in thread: Suzuki K Poulose: "Re: [PATCH v2] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]