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Date:   Mon, 31 Oct 2022 14:38:58 +0100
From:   Petr Vorel <pvorel@suse.cz>
To:     linux-nfs@vger.kernel.org
Cc:     Chuck Lever <chuck.lever@oracle.com>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        NeilBrown <neilb@suse.com>, Steve Dickson <steved@redhat.com>,
        ltp@lists.linux.it
Subject: LTP test regression on exportfs in kernel 6.0
Message-ID: <Y1/P8gDAcWC/+VR3@pevik>
Reply-To: Petr Vorel <pvorel@suse.cz>
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Hi all,

LTP tests got broken on kernel 6.0. During test cleanup it hangs on exportfs
(high load). I tested it both on nfs-utils 2.6.2, the same userspace, the
version of the tests (obviously), it looks really like kernel related regre=
ssion.

# Simple reproducer
git clone https://github.com/linux-test-project/ltp.git
# install dependencies with your distro in ci/*.sh
make autotools && ./configure && make -j$(getconf _NPROCESSORS_ONLN) && mak=
e install
export LTPROOT=3D/opt/ltp; PATH=3D"/opt/ltp/testcases/bin:$PATH" nfs02.sh -=
v 4 -t tcp
TMPDIR=3D"/var/tmp" nfs02.sh -v 4 -t tcp

# Example on kernel oops on openSUSE
[  304.772002] Initializing XFRM netlink socket
[  304.833577] IPv6: ADDRCONF(NETDEV_CHANGE): ltp_ns_veth1: link becomes re=
ady
[  304.833604] IPv6: ADDRCONF(NETDEV_CHANGE): ltp_ns_veth2: link becomes re=
ady
[  304.957269] FS-Cache: Loaded
[  305.002821] Key type dns_resolver registered
[  305.153926] NFS: Registering the id_resolver key type
[  305.153942] Key type id_resolver registered
[  305.153943] Key type id_legacy registered
[  326.587135] rcu: INFO: rcu_preempt self-detected stall on CPU
[  326.587168] rcu: 	0-....: (5249 ticks this GP) idle=3Dcf74/1/0x400000000=
0000000 softirq=3D7256/7256 fqs=3D2484
[  326.587187] 	(t=3D5250 jiffies g=3D4009 q=3D388 ncpus=3D2)
[  326.587191] NMI backtrace for cpu 0
[  326.587192] CPU: 0 PID: 1008 Comm: exportfs Not tainted 5.19.0 #4
[  326.587195] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS =
rel-1.16.0-0-gd239552-rebuilt.opensuse.org 04/01/2014
[  326.587199] Call Trace:
[  326.587212]  <IRQ>
[  326.587216]  dump_stack_lvl+0x45/0x5e
[  326.587231]  nmi_cpu_backtrace.cold+0x30/0x76
[  326.587234]  ? lapic_can_unplug_cpu+0x80/0x80
[  326.587241]  nmi_trigger_cpumask_backtrace+0x10c/0x140
[  326.587252]  rcu_dump_cpu_stacks+0xf8/0x130
[  326.587260]  rcu_sched_clock_irq.cold+0x67/0x2f8
[  326.587270]  ? raw_notifier_call_chain+0x41/0x60
[  326.587275]  ? timekeeping_update+0xde/0x130
[  326.587280]  ? __cgroup_account_cputime_field+0x5d/0x90
[  326.587286]  update_process_times+0x62/0x90
[  326.587291]  tick_sched_handle+0x22/0x60
[  326.587300]  tick_sched_timer+0x71/0x90
[  326.587303]  ? tick_sched_do_timer+0xa0/0xa0
[  326.587306]  __hrtimer_run_queues+0x127/0x2c0
[  326.587310]  hrtimer_interrupt+0x106/0x220
[  326.587313]  __sysvec_apic_timer_interrupt+0x7c/0x170
[  326.587319]  sysvec_apic_timer_interrupt+0x9d/0xd0
[  326.587328]  </IRQ>
[  326.587328]  <TASK>
[  326.587329]  asm_sysvec_apic_timer_interrupt+0x16/0x20
[  326.587339] RIP: 0010:__nfsd_file_cache_purge+0x54/0xd0 [nfsd]
[  326.587374] Code: 48 89 24 24 48 89 64 24 08 e8 88 3e e8 e5 48 8d 7c 24 =
10 e8 ae 53 e8 e5 48 8d 7c 24 10 e8 04 4d e8 e5 48 89 c5 48 85 c0 74 27 <48=
> 81 fd 00 f0 ff ff 77 55 48 85 db 74 06 48 39 5d 38 75 ec 48 89
[  326.587376] RSP: 0018:ffffbfe84100bd88 EFLAGS: 00000202
[  326.587378] RAX: ffff9dcd01f9a3a8 RBX: ffff9dcd0af86600 RCX: ffffffffc0c=
eabc0
[  326.587380] RDX: 0000000000000000 RSI: 000000000000008c RDI: ffffbfe8410=
0bd98
[  326.587381] RBP: ffff9dcd01f9a3a8 R08: 0000000000000000 R09: ffffffffa6f=
d2b75
[  326.587382] R10: 0000000000000000 R11: ffffbfe84100bd98 R12: ffffbfe8410=
0bf08
[  326.587383] R13: 00007fff97dc3a20 R14: ffffbfe84100bf08 R15: 00000000000=
00000
[  326.587385]  ? _raw_spin_unlock+0x15/0x30
[  326.587393]  ? __nfsd_file_cache_purge+0x4c/0xd0 [nfsd]
[  326.587410]  ? _raw_spin_unlock+0x15/0x30
[  326.587412]  expkey_flush+0x2a/0x40 [nfsd]
[  326.587427]  write_flush.constprop.0+0xf4/0x140 [sunrpc]
[  326.587460]  proc_reg_write+0x4e/0x90
[  326.587470]  vfs_write+0xc3/0x3d0
[  326.587478]  ? preempt_count_add+0x4d/0xa0
[  326.587482]  ? fd_install+0x5c/0xe0
[  326.587489]  ksys_write+0x5f/0xe0
[  326.587492]  do_syscall_64+0x38/0xc0
[  326.587496]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[  326.587501] RIP: 0033:0x7f6f908063f3
[  326.587505] Code: 8b 15 21 9a 0f 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff =
eb b7 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 01 00 00 00 0f 05 <48=
> 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 48 89 54 24 18
[  326.587506] RSP: 002b:00007fff97dc3a08 EFLAGS: 00000246 ORIG_RAX: 000000=
0000000001
[  326.587508] RAX: ffffffffffffffda RBX: 000056110e2f8dd0 RCX: 00007f6f908=
063f3
[  326.587509] RDX: 000000000000000b RSI: 00007fff97dc3a20 RDI: 00000000000=
00006
[  326.587510] RBP: 000056110e2f500e R08: 00007f6f908b83e0 R09: 00000000000=
00000
[  326.587512] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff97d=
c3ad0
[  326.587514] R13: 00007fff97dc3a20 R14: 0000000000000006 R15: 000056110e2=
f4fef
[  326.587517]  </TASK>

# Bug on Debian config with openSUSE setup looks fairly similar:
[ 7972.371206] watchdog: BUG: soft lockup - CPU#0 stuck for 44s! [exportfs:=
1180]
[ 7972.371250] Modules linked in: rpcsec_gss_krb5 nfsv4 dns_resolver nfs fs=
cache netfs xfrm_user xfrm_algo veth intel_rapl_msr intel_rapl_common intel=
_pmc_core_pltdrv intel_pmc_core kvm_intel kvm irqbypass ghash_clmulni_intel=
 snd_hda_codec_generic ledtrig_audio aesni_intel crypto_simd cryptd rapl qx=
l evdev snd_hda_intel drm_ttm_helper snd_intel_dspcfg serio_raw pcspkr snd_=
intel_sdw_acpi ttm joydev virtio_console virtio_balloon snd_hda_codec sg dr=
m_kms_helper snd_hda_core snd_hwdep snd_pcm qemu_fw_cfg snd_timer snd sound=
core button nfsd auth_rpcgss nfs_acl lockd grace sunrpc drm fuse configfs v=
irtio_rng rng_core ip_tables x_tables autofs4 btrfs blake2b_generic xor rai=
d6_pq zstd_compress libcrc32c crc32c_generic hid_generic usbhid hid dm_mod =
virtio_net net_failover virtio_blk failover sr_mod cdrom crct10dif_pclmul c=
rct10dif_common crc32_pclmul crc32c_intel psmouse ata_generic uhci_hcd ehci=
_pci ehci_hcd ata_piix usbcore libata usb_common virtio_pci virtio_pci_lega=
cy_dev virtio_pci_modern_dev
[ 7972.371310]  virtio virtio_ring scsi_mod i2c_piix4 scsi_common floppy
[ 7972.371315] CPU: 0 PID: 1180 Comm: exportfs Not tainted 6.0.1 #2
[ 7972.371317] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS =
rel-1.16.0-0-gd239552-rebuilt.opensuse.org 04/01/2014
[ 7972.371318] RIP: 0010:__nfsd_file_cache_purge+0x54/0xd0 [nfsd]
[ 7972.371344] Code: 48 89 24 24 48 89 64 24 08 e8 38 23 46 d4 48 8d 7c 24 =
10 e8 5e 38 46 d4 48 8d 7c 24 10 e8 b4 31 46 d4 48 89 c5 48 85 c0 74 27 <48=
> 81 fd 00 f0 ff ff 77 55 48 85 db 74 06 48 39 5d 38 75 ec 48 89
[ 7972.371348] RSP: 0018:ffffc05241067d88 EFLAGS: 00000202
[ 7972.371350] RAX: ffff9bd3c5380618 RBX: ffff9bd3f260d500 RCX: ffffffffc0b=
0cbc0
[ 7972.371351] RDX: 0000000000000000 RSI: 00000000000000b2 RDI: ffffc052410=
67d98
[ 7972.371352] RBP: ffff9bd3c5380618 R08: 0000000000000000 R09: ffffffff953=
d3aa5
[ 7972.371353] R10: 0000000000000000 R11: ffffc05241067d98 R12: ffffc052410=
67f08
[ 7972.371354] R13: 00007ffd820fd9f0 R14: ffffc05241067f08 R15: 00000000000=
00000
[ 7972.371356] FS:  00007fd3e4d1c740(0000) GS:ffff9bd3fec00000(0000) knlGS:=
0000000000000000
[ 7972.371357] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 7972.371358] CR2: 00007fd3e4d8a040 CR3: 00000000089a6005 CR4: 00000000003=
70ef0
[ 7972.371362] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 00000000000=
00000
[ 7972.371363] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 00000000000=
00400
[ 7972.371364] Call Trace:
[ 7972.371367]  <TASK>
[ 7972.371376]  ? _raw_spin_unlock+0x15/0x30
[ 7972.371383]  expkey_flush+0x2a/0x40 [nfsd]
[ 7972.371402]  write_flush.constprop.0+0xf4/0x140 [sunrpc]
[ 7972.371440]  proc_reg_write+0x4e/0x90
[ 7972.371443]  vfs_write+0xc3/0x3d0
[ 7972.371446]  ? preempt_count_add+0x4d/0xa0
[ 7972.371450]  ? fd_install+0x5c/0xe0
[ 7972.371452]  ksys_write+0x5f/0xe0
[ 7972.371454]  do_syscall_64+0x38/0xc0
[ 7972.371458]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 7972.371460] RIP: 0033:0x7fd3e4e193f3
[ 7972.371462] Code: 8b 15 21 9a 0f 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff =
eb b7 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 01 00 00 00 0f 05 <48=
> 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 48 89 54 24 18
[ 7972.371464] RSP: 002b:00007ffd820fd9d8 EFLAGS: 00000246 ORIG_RAX: 000000=
0000000001
[ 7972.371466] RAX: ffffffffffffffda RBX: 00005559a20e4dd0 RCX: 00007fd3e4e=
193f3
[ 7972.371467] RDX: 000000000000000b RSI: 00007ffd820fd9f0 RDI: 00000000000=
00006
[ 7972.371468] RBP: 00005559a20e100e R08: 00007fd3e4ecb3e0 R09: 00000000000=
00000
[ 7972.371469] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd820=
fdaa0
[ 7972.371470] R13: 00007ffd820fd9f0 R14: 0000000000000006 R15: 00005559a20=
e0fef
[ 7972.371473]  </TASK>

I guess I don't need to turn any debugging with rpcdebug at this point (eno=
ugh
info from this), right?

It looks like to be config related, because it's broken with openSUSE confi=
g,
but not with Debian config. Building with Debian config, but changing just =
these
NFS specific options it also fails:

# config difference Debian (-) vs openSUSE (+)
-CONFIG_NFS_DISABLE_UDP_SUPPORT=3Dy
+# CONFIG_NFS_DISABLE_UDP_SUPPORT is not set
-# CONFIG_NFSD_SCSILAYOUT is not set
-# CONFIG_NFSD_FLEXFILELAYOUT is not set
-# CONFIG_NFSD_V4_2_INTER_SSC is not set
+CONFIG_NFSD_SCSILAYOUT=3Dy
+CONFIG_NFSD_FLEXFILELAYOUT=3Dy
+CONFIG_NFSD_V4_2_INTER_SSC=3Dy

I suspect it was caused by e394ff83bbca ("Merge tag 'nfsd-6.0' of
git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux") [1], but I need to
finish bisecting to be sure (it was merged earlier than aeb6e6ac18c7 ("Merg=
e tag
'nfs-for-5.20-1' of git://git.linux-nfs.org/projects/trondmy/linux-nfs") [2=
],
both are broken).

Kind regards,
Petr

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/comm=
it/?id=3De394ff83bbca1c72427b1feb5c6b9d4dad832f01
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/comm=
it/?id=3Daeb6e6ac18c73ec287b3b1e2c913520699358c13