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From: Yafang Shao <laoar.shao@gmail.com>
Date: Thu, 30 May 2024 17:24:21 +0800
Message-ID: <CALOAHbC8NM7R-pKvPW6m4fnn_8BQZuPjJrNZaEN=sg67Gp+NGQ@mail.gmail.com>
Subject: Re: [PATCH 1/1] mm: protect xa split stuff under lruvec->lru_lock
 during migration
To: Zhaoyang Huang <huangzhaoyang@gmail.com>
Cc: Marcin Wanat <private@marcinwanat.pl>, Dave Chinner <david@fromorbit.com>, 
	Andrew Morton <akpm@linux-foundation.org>, "zhaoyang.huang" <zhaoyang.huang@unisoc.com>, 
	Alex Shi <alexs@kernel.org>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, 
	Hugh Dickins <hughd@google.com>, Baolin Wang <baolin.wang@linux.alibaba.com>, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org, steve.kang@unisoc.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Thu, May 30, 2024 at 4:57=E2=80=AFPM Zhaoyang Huang <huangzhaoyang@gmail=
com> wrote:
>
> On Thu, May 30, 2024 at 4:49=E2=80=AFPM Yafang Shao <laoar.shao@gmail.com=
> wrote:
> >
> > On Tue, May 21, 2024 at 3:42=E2=80=AFAM Marcin Wanat <private@marcinwan=
at.pl> wrote:
> > >
> > > On 15.04.2024 03:50, Zhaoyang Huang wrote:
> > > > On Mon, Apr 15, 2024 at 8:09=E2=80=AFAM Dave Chinner <david@fromorb=
it.com> > wrote: >> >> On Sat, Apr 13, 2024 at 10:01:27AM +0800, Zhaoyang
> > > Huang wrote: >>> loop Dave, since he has ever helped set up an
> > > reproducer in >>> https://lore.kernel.org/linux- >>>
> > > mm/20221101071721.GV2703033@dread.disaster.area/ @Dave Chinner , >>> =
I
> > > would like to ask for your kindly help on if you can verify >>> this
> > > patch on your environment if convenient. Thanks a lot. >> >> I don't
> > > have the test environment from 18 months ago available any >> more.
> > > Also, I haven't seen this problem since that specific test >>
> > > environment tripped over the issue. Hence I don't have any way of >>
> > > confirming that the problem is fixed, either, because first I'd >> ha=
ve
> > > to reproduce it... > Thanks for the information. I noticed that you
> > > reported another soft > lockup which is related to xas_load since
> > > NOV.2023. This patch is > supposed to be helpful for this. With regar=
d
> > > to the version timing, > this commit is actually a revert of <mm/thp:
> > > narrow lru locking> > b6769834aac1d467fa1c71277d15688efcbb4d76 which =
is
> > > merged before > v5.15. > > For saving your time, a brief description
> > > below. IMO, b6769834aa > introduce a potential stall between freeze t=
he
> > > folio's refcnt and > store it back to 2, which have the
> > > xas_load->folio_try_get_rcu loops > as livelock if it stalls the
> > > lru_lock's holder. > > b6769834aa split_huge_page_to_list -
> > > spin_lock(lru_lock) > xas_split(&xas, folio,order)
> > > folio_refcnt_freeze(folio, 1 + > folio_nr_pages(folio0) +
> > > spin_lock(lru_lock) xas_store(&xas, > offset++, head+i)
> > > page_ref_add(head, 2) spin_unlock(lru_lock) > > Sorry in advance if t=
he
> > > above doesn't make sense, I am just a > developer who is also sufferi=
ng
> > > from this bug and trying to fix it
> > > I am experiencing a similar error on dozens of hosts, with stack trac=
es
> > > that are all similar:
> > >
> > > [627163.727746] watchdog: BUG: soft lockup - CPU#77 stuck for 22s!
> > > [file_get:953301]
> > > [627163.727778] Modules linked in: xt_set ip_set_hash_net ip_set xt_C=
T
> > > xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_compat
> > > nf_tables nfnetlink sr_mod cdrom rfkill vfat fat intel_rapl_msr
> > > intel_rapl_common intel_uncore_frequency intel_uncore_frequency_commo=
n
> > > isst_if_common skx_edac nfit libnvdimm x86_pkg_temp_thermal
> > > intel_powerclamp coretemp ipmi_ssif kvm_intel kvm irqbypass mlx5_ib r=
apl
> > > iTCO_wdt intel_cstate intel_pmc_bxt ib_uverbs iTCO_vendor_support
> > > dell_smbios dcdbas i2c_i801 intel_uncore uas ses mei_me ib_core
> > > dell_wmi_descriptor wmi_bmof pcspkr enclosure lpc_ich usb_storage
> > > i2c_smbus acpi_ipmi mei intel_pch_thermal ipmi_si ipmi_devintf
> > > ipmi_msghandler acpi_power_meter joydev tcp_bbr fuse xfs libcrc32c ra=
id1
> > > sd_mod sg mlx5_core crct10dif_pclmul crc32_pclmul crc32c_intel
> > > polyval_clmulni mgag200 polyval_generic drm_kms_helper mlxfw
> > > drm_shmem_helper ahci nvme mpt3sas tls libahci ghash_clmulni_intel
> > > nvme_core psample drm igb t10_pi raid_class pci_hyperv_intf dca libat=
a
> > > scsi_transport_sas i2c_algo_bit wmi
> > > [627163.727841] CPU: 77 PID: 953301 Comm: file_get Kdump: loaded
> > > Tainted: G             L     6.6.30.el9 #2
> > > [627163.727844] Hardware name: Dell Inc. PowerEdge R740xd/08D89F, BIO=
S
> > > 2.21.2 02/19/2024
> > > [627163.727847] RIP: 0010:xas_descend+0x1b/0x70
> > > [627163.727857] Code: 57 10 48 89 07 48 c1 e8 20 48 89 57 08 c3 cc 0f=
 b6
> > > 0e 48 8b 47 08 48 d3 e8 48 89 c1 83 e1 3f 89 c8 48 83 c0 04 48 8b 44 =
c6
> > > 08 <48> 89 77 18 48 89 c2 83 e2 03 48 83 fa 02 74 0a 88 4f 12 c3 48 8=
3
> > > [627163.727859] RSP: 0018:ffffc90034a67978 EFLAGS: 00000206
> > > [627163.727861] RAX: ffff888e4f971242 RBX: ffffc90034a67a98 RCX:
> > > 0000000000000020
> > > [627163.727863] RDX: 0000000000000002 RSI: ffff88a454546d80 RDI:
> > > ffffc90034a67990
> > > [627163.727865] RBP: fffffffffffffffe R08: fffffffffffffffe R09:
> > > 0000000000008820
> > > [627163.727867] R10: 0000000000008820 R11: 0000000000000000 R12:
> > > ffffc90034a67a20
> > > [627163.727868] R13: ffffc90034a67a18 R14: ffffea00873e8000 R15:
> > > ffffc90034a67a18
> > > [627163.727870] FS:  00007fc5e503b740(0000) GS:ffff88bfefd80000(0000)
> > > knlGS:0000000000000000
> > > [627163.727871] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [627163.727873] CR2: 000000005fb87b6e CR3: 00000022875e8006 CR4:
> > > 00000000007706e0
> > > [627163.727875] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> > > 0000000000000000
> > > [627163.727876] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> > > 0000000000000400
> > > [627163.727878] PKRU: 55555554
> > > [627163.727879] Call Trace:
> > > [627163.727882]  <IRQ>
> > > [627163.727886]  ? watchdog_timer_fn+0x22a/0x2a0
> > > [627163.727892]  ? softlockup_fn+0x70/0x70
> > > [627163.727895]  ? __hrtimer_run_queues+0x10f/0x2a0
> > > [627163.727903]  ? hrtimer_interrupt+0x106/0x240
> > > [627163.727906]  ? __sysvec_apic_timer_interrupt+0x68/0x170
> > > [627163.727913]  ? sysvec_apic_timer_interrupt+0x9d/0xd0
> > > [627163.727917]  </IRQ>
> > > [627163.727918]  <TASK>
> > > [627163.727920]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
> > > [627163.727927]  ? xas_descend+0x1b/0x70
> > > [627163.727930]  xas_load+0x2c/0x40
> > > [627163.727933]  xas_find+0x161/0x1a0
> > > [627163.727937]  find_get_entries+0x77/0x1d0
> > > [627163.727944]  truncate_inode_pages_range+0x244/0x3f0
> > > [627163.727950]  truncate_pagecache+0x44/0x60
> > > [627163.727955]  xfs_setattr_size+0x168/0x490 [xfs]
> > > [627163.728074]  xfs_vn_setattr+0x78/0x140 [xfs]
> > > [627163.728153]  notify_change+0x34f/0x4f0
> > > [627163.728158]  ? _raw_spin_lock+0x13/0x30
> > > [627163.728165]  ? do_truncate+0x80/0xd0
> > > [627163.728169]  do_truncate+0x80/0xd0
> > > [627163.728172]  do_open+0x2ce/0x400
> > > [627163.728177]  path_openat+0x10d/0x280
> > > [627163.728181]  do_filp_open+0xb2/0x150
> > > [627163.728186]  ? check_heap_object+0x34/0x190
> > > [627163.728189]  ? __check_object_size.part.0+0x5a/0x130
> > > [627163.728194]  do_sys_openat2+0x92/0xc0
> > > [627163.728197]  __x64_sys_openat+0x53/0x90
> > > [627163.728200]  do_syscall_64+0x35/0x80
> > > [627163.728206]  entry_SYSCALL_64_after_hwframe+0x4b/0xb5
> > > [627163.728210] RIP: 0033:0x7fc5e493e7fb
> > > [627163.728213] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25=
 18
> > > 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 =
0f
> > > 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 54 24 28 64 48 2b 14 2=
5
> > > [627163.728215] RSP: 002b:00007ffdd4e300e0 EFLAGS: 00000246 ORIG_RAX:
> > > 0000000000000101
> > > [627163.728218] RAX: ffffffffffffffda RBX: 00007ffdd4e30180 RCX:
> > > 00007fc5e493e7fb
> > > [627163.728220] RDX: 0000000000000241 RSI: 00007ffdd4e30180 RDI:
> > > 00000000ffffff9c
> > > [627163.728221] RBP: 00007ffdd4e30180 R08: 00007fc5e4600040 R09:
> > > 0000000000000001
> > > [627163.728223] R10: 00000000000001b6 R11: 0000000000000246 R12:
> > > 0000000000000241
> > > [627163.728224] R13: 0000000000000000 R14: 00007fc5e4662fa8 R15:
> > > 0000000000000000
> > > [627163.728227]  </TASK>
> > >
> > > I have around 50 hosts handling high I/O (each with 20Gbps+ uplinks
> > > and multiple NVMe drives), running RockyLinux 8/9. The stock RHEL
> > > kernel 8/9 is NOT affected, and the long-term kernel 5.15.X is NOT af=
fected.
> > > However, with long-term kernels 6.1.XX and 6.6.XX,
> > > (tested at least 10 different versions), this lockup always appears
> > > after 2-30 days, similar to the report in the original thread.
> > > The more load (for example, copying a lot of local files while
> > > serving 20Gbps traffic), the higher the chance that the bug will appe=
ar.
> > >
> > > I haven't been able to reproduce this during synthetic tests,
> > > but it always occurs in production on 6.1.X and 6.6.X within 2-30 day=
s.
> >
> > We encountered a similar issue several months ago. Some of our
> > production servers crashed within days after deploying the 6.1.y
> > stable kernel. The soft lock info as follows,
> >
> > [282879.612238] watchdog: BUG: soft lockup - CPU#65 stuck for 101s!
> > [container-execu:1572375]
> > [282879.612513] Modules linked in: ebtable_filter ebtables xt_DSCP
> > iptable_mangle iptable_raw xt_CT cls_bpf sch_ingress raw_diag
> > unix_diag tcp_diag udp_diag inet_diag iptable_filter bpfilter
> > xt_conntrack nf_nat nf_conntrack_netlink nfnetlink nf_conntrack
> > nf_defrag_ipv6 nf_defrag_ipv4 bpf_preload binfmt_misc cuse fuse
> > overlay af_packet bonding intel_rapl_msr intel_rapl_common
> > 64_edac kvm_amd kvm irqbypass crct10dif_pclmul crc32_pclmul
> > polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3
> > aesni_intel crypto_simd cryptd rapl pcspkr vfat fat xfs mlx5_ib(O)
> > ib_uverbs(O) input_leds ib_core(O) sg ccp ptdma i2c_piix4 k10temp
> > acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler acpi_cpufreq ip_tables
> > ext4 mbcache crc32c_intel jbd2 mlx5_core(O) mlxfw(O) pci_hyperv_intf
> > psample mlxdevm(O) mlx_compat(O) tls nvme ptp pps_core nvme_core
> > sd_mod t10_pi ahci libahci libata
> > [282879.612571] CPU: 65 PID: 1572375 Comm: container-execu Kdump:
> > loaded Tainted: G        W  O L     6.1.38-rc3 #rc3.pdd
> > [282879.612574] Hardware name: New H3C Technologies Co., Ltd. H3C
> > UniServer R4950 G5/RS45M2C9S, BIOS 5.30 06/30/2021
> > [282879.612576] RIP: 0010:xas_descend+0x18/0x80
> > [282879.612583] Code: b6 e8 ec de 05 00 cc cc cc cc cc cc cc cc cc cc
> > cc cc 0f b6 0e 48 8b 57 08 48 d3 ea 83 e2 3f 89 d0 48 83 c0 04 48 8b
> > 44 c6 08 <48> 89 77 18 48 89 c1 83 e1 03 48 83 f9 02 75 08 48 3d fd 00
> > 00 00
> > [282879.612586] RSP: 0018:ffffad700b247c40 EFLAGS: 00000202
> > [282879.612588] RAX: ffff91d247a75d8a RBX: fffffffffffffffe RCX:
> > 0000000000000006
> > [282879.612589] RDX: 0000000000000026 RSI: ffff91d473cb7b30 RDI:
> > ffffad700b247c68
> > [282879.612591] RBP: ffffad700b247c48 R08: 0000000000000003 R09:
> > fffffffffffffffe
> > [282879.612592] R10: 0000000000001990 R11: 0000000000000003 R12:
> > ffffad700b247cf8
> > [282879.612593] R13: ffffad700b247d70 R14: ffffad700b247cf8 R15:
> > ffffdfcd2c778000
> > [282879.612594] FS:  00007f5f576fb740(0000) GS:ffff922df0840000(0000)
> > knlGS:0000000000000000
> > [282879.612596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [282879.612597] CR2: 00007fe797100600 CR3: 0000002b2468e000 CR4:
> > 0000000000350ee0
> > [282879.612599] Call Trace:
> > [282879.612601]  <IRQ>
> > [282879.612605]  ? show_regs.cold+0x1a/0x1f
> > [282879.612610]  ? watchdog_timer_fn+0x1c4/0x220
> > [282879.612614]  ? softlockup_fn+0x30/0x30
> > [282879.612616]  ? __hrtimer_run_queues+0xa2/0x2b0
> > [282879.612620]  ? hrtimer_interrupt+0x109/0x220
> > [282879.612622]  ? __sysvec_apic_timer_interrupt+0x5e/0x110
> > [282879.612625]  ? sysvec_apic_timer_interrupt+0x7b/0x90
> > [282879.612629]  </IRQ>
> > [282879.612630]  <TASK>
> > [282879.612631]  ? asm_sysvec_apic_timer_interrupt+0x1b/0x20
> > [282879.612640]  ? xas_descend+0x18/0x80
> > [282879.612641]  ? xas_load+0x35/0x40
> > [282879.612643]  xas_find+0x197/0x1d0
> > [282879.612645]  find_get_entries+0x6e/0x170
> > [282879.612649]  truncate_inode_pages_range+0x294/0x4c0
> > [282879.612655]  ? __xfs_trans_commit+0x13c/0x3e0 [xfs]
> > [282879.612787]  ? kvfree+0x2c/0x40
> > [282879.612791]  ? trace_hardirqs_off+0x36/0xf0
> > [282879.612795]  truncate_inode_pages_final+0x44/0x50
> > [282879.612798]  evict+0x177/0x190
> > [282879.612802]  iput.part.0+0x183/0x1e0
> > [282879.612804]  iput+0x1c/0x30
> > [282879.612806]  do_unlinkat+0x1c7/0x2c0
> > [282879.612810]  __x64_sys_unlinkat+0x38/0x70
> > [282879.612812]  do_syscall_64+0x38/0x90
> > [282879.612815]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > [282879.612818] RIP: 0033:0x7f5f56cf120d
> > [282879.612827] Code: 69 5c 2d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e
> > 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 63 d2 48 63 ff b8 07 01 00
> > 00 0f 05 <48> 3d 00 f0 ff ff 77 02 f3 c3 48 8b 15 32 5c 2d 00 f7 d8 64
> > 89 02
> > [282879.612828] RSP: 002b:00007fff30375c48 EFLAGS: 00000206 ORIG_RAX:
> > 0000000000000107
> > [282879.612830] RAX: ffffffffffffffda RBX: 0000000000000003 RCX:
> > 00007f5f56cf120d
> > [282879.612831] RDX: 0000000000000000 RSI: 0000000001640403 RDI:
> > 0000000000000003
> > [282879.612832] RBP: 0000000001640403 R08: 0000000000000000 R09:
> > 0000000001640403
> > [282879.612833] R10: 0000000000000100 R11: 0000000000000206 R12:
> > 0000000000000003
> > [282879.612834] R13: 000000000163c5c0 R14: 00007fff30375c80 R15:
> > 0000000000000000
> > [282879.612836]  </TASK>
> >
> >
> > Unfortunately, we couldn't reproduce the issue on our test servers. We
> > worked around it by disabling CONFIG_XARRAY_MULTI. Since then, these
> > production servers have been running smoothly for several months.
> >
> > > If anyone can provide a patch, I can test it on multiple machines
> > > over the next few days.
> It is highly appreciated that you could help to try below one which
> works on my v6.6 based android. However, there is a hard lockup
> reported on an ongoing regression test(not sure if caused by this
> patch yet). Thank you!

I'm sorry to inform you that our users are unwilling to experiment
with these changes on our production servers again, and I am unable to
reproduce the issue on our test servers. I am reporting this issue to
highlight to the community that it is indeed a serious problem, and we
should consider it carefully.

>
> mm/huge_memory.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 064fbd90822b..5899906c326a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2498,7 +2498,7 @@ static void __split_huge_page(struct page *page,
> struct list_head *list,
>  {
>   struct folio *folio =3D page_folio(page);
>   struct page *head =3D &folio->page;
> - struct lruvec *lruvec;
> + struct lruvec *lruvec =3D folio_lruvec(folio);
>   struct address_space *swap_cache =3D NULL;
>   unsigned long offset =3D 0;
>   unsigned int nr =3D thp_nr_pages(head);
> @@ -2513,9 +2513,6 @@ static void __split_huge_page(struct page *page,
> struct list_head *list,
>   xa_lock(&swap_cache->i_pages);
>   }
>
> - /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
> - lruvec =3D folio_lruvec_lock(folio);
> -
>   ClearPageHasHWPoisoned(head);
>
>   for (i =3D nr - 1; i >=3D 1; i--) {
> @@ -2541,9 +2538,6 @@ static void __split_huge_page(struct page *page,
> struct list_head *list,
>   }
>
>   ClearPageCompound(head);
> - unlock_page_lruvec(lruvec);
> - /* Caller disabled irqs, so they are still disabled here */
> -
>   split_page_owner(head, nr);
>
>   /* See comment in __split_huge_page_tail() */
> @@ -2560,7 +2554,6 @@ static void __split_huge_page(struct page *page,
> struct list_head *list,
>   page_ref_add(head, 2);
>   xa_unlock(&head->mapping->i_pages);
>   }
> - local_irq_enable();
>
>   if (nr_dropped)
>   shmem_uncharge(head->mapping->host, nr_dropped);
> @@ -2631,6 +2624,7 @@ int split_huge_page_to_list(struct page *page,
> struct list_head *list)
>   int extra_pins, ret;
>   pgoff_t end;
>   bool is_hzp;
> + struct lruvec *lruvec;
>
>   VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
>   VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
> @@ -2714,6 +2708,14 @@ int split_huge_page_to_list(struct page *page,
> struct list_head *list)
>
>   /* block interrupt reentry in xa_lock and spinlock */
>   local_irq_disable();
> +
> + /*
> + * take lruvec's lock before freeze the folio to prevent the folio
> + * remains in the page cache with refcnt =3D=3D 0, which could lead to
> + * find_get_entry enters livelock by iterating the xarray.
> + */
> + lruvec =3D folio_lruvec_lock(folio);
> +
>   if (mapping) {
>   /*
>   * Check if the folio is present in page cache.
> @@ -2748,12 +2750,16 @@ int split_huge_page_to_list(struct page *page,
> struct list_head *list)
>   }
>
>   __split_huge_page(page, list, end);
>
> > >
> >
> >
> > --
> > Regards
> > Yafang


--=20
Regards
Yafang