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Message-ID: <7d244882d769e377b06f39234bd5ee7dddb72a55.camel@kernel.org>
Subject: Re: nfsd hangs and nfsd_break_deleg_cb+0x170/0x190 warning
From: Jeff Layton <jlayton@kernel.org>
To: Rik Theys <Rik.Theys@esat.kuleuven.be>, Linux Nfs
	 <linux-nfs@vger.kernel.org>
Date: Mon, 18 Mar 2024 17:54:05 -0400
In-Reply-To: <41325088-aa6d-4dcf-b105-8994350168c3@esat.kuleuven.be>
References: <66c98f4c-5e52-4fa3-8a2c-9379cfec2a9a@esat.kuleuven.be>
	 <44c2101e756f7c3b876fb9c58da3ebd089dc14d5.camel@kernel.org>
	 <e3ba6e04-ea06-4035-8546-639f11d6b79c@esat.kuleuven.be>
	 <41325088-aa6d-4dcf-b105-8994350168c3@esat.kuleuven.be>
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Content-Type: text/plain; charset="UTF-8"
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On Mon, 2024-03-18 at 22:15 +0100, Rik Theys wrote:
> Hi,
>=20
> On 3/18/24 21:21, Rik Theys wrote:
> > Hi Jeff,
> >=20
> > On 3/12/24 13:47, Jeff Layton wrote:
> > > On Tue, 2024-03-12 at 13:24 +0100, Rik Theys wrote:
> > > > Hi Jeff,
> > > >=20
> > > > On 3/12/24 12:22, Jeff Layton wrote:
> > > > > On Mon, 2024-03-11 at 19:43 +0100, Rik Theys wrote:
> > > > > > Since a few weeks our Rocky Linux 9 NFS server has periodically=
=20
> > > > > > logged hung nfsd tasks. The initial effect was that some client=
s=20
> > > > > > could no longer access the NFS server. This got worse and worse=
=20
> > > > > > (probably as more nfsd threads got blocked) and we had to resta=
rt=20
> > > > > > the server. Restarting the server also failed as the NFS server=
=20
> > > > > > service could no longer be stopped.
> > > > > >=20
> > > > > > The initial kernel we noticed this behavior on was=20
> > > > > > kernel-5.14.0-362.18.1.el9_3.x86_64. Since then we've installed=
=20
> > > > > > kernel-5.14.0-419.el9.x86_64 from CentOS Stream 9. The same iss=
ue=20
> > > > > > happened again on this newer kernel version:
> > > 419 is fairly up to date with nfsd changes. There are some known bugs
> > > around callbacks, and there is a draft MR in flight to fix it.
> > >=20
> > > What kernel were you on prior to 5.14.0-362.18.1.el9_3.x86_64 ? If we
> > > can bracket the changes around a particular version, then that might
> > > help identify the problem.
> > >=20
> > > > > > [Mon Mar 11 14:10:08 2024] =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
Not tainted 5.14.0-419.el9.x86_64 #1
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] "echo 0 >=20
> > > > > > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024]task:nfsd=C2=A0 =C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0state:D stack:0=
=20
> > > > > > =C2=A0=C2=A0=C2=A0=C2=A0pid:8865 =C2=A0ppid:2 =C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0flags:0x00004000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] Call Trace:
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0<TASK>
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__schedule+0x21b/=
0x550
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0schedule+0x2d/0x7=
0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0schedule_timeout+=
0x11f/0x160
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? select_idle_sib=
ling+0x28/0x430
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? wake_affine+0x6=
2/0x1f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__wait_for_common=
+0x90/0x1d0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_schedule_=
timeout+0x10/0x10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__flush_workqueue=
+0x13a/0x3f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd4_shutdown_ca=
llback+0x49/0x120=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? nfsd4_cld_remov=
e+0x54/0x1d0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0?=20
> > > > > > nfsd4_return_all_client_layouts+0xc4/0xf0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? nfsd4_shutdown_=
copy+0x68/0xc0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__destroy_client+=
0x1f3/0x290 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd4_exchange_id=
+0x75f/0x770 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? nfsd4_decode_op=
aque+0x3a/0x90 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd4_proc_compou=
nd+0x44b/0x700 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd_dispatch+0x9=
4/0x1c0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0svc_process_commo=
n+0x2ec/0x660=20
> > > > > > [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_nfsd_disp=
atch+0x10/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_nfsd+0x10=
/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0svc_process+0x12d=
/0x170 [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd+0x84/0xb0 [n=
fsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0kthread+0xdd/0x10=
0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_kthread+0=
x10/0x10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0ret_from_fork+0x2=
9/0x50
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0</TASK>
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] INFO: task nfsd:8866 bl=
ocked for=20
> > > > > > more than 122 seconds.
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0Not tainted=20
> > > > > > 5.14.0-419.el9.x86_64 #1
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] "echo 0 >=20
> > > > > > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024]task:nfsd=C2=A0 =C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0state:D stack:0=
=20
> > > > > > =C2=A0=C2=A0=C2=A0=C2=A0pid:8866 =C2=A0ppid:2 =C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0flags:0x00004000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] Call Trace:
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0<TASK>
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__schedule+0x21b/=
0x550
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0schedule+0x2d/0x7=
0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0schedule_timeout+=
0x11f/0x160
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? select_idle_sib=
ling+0x28/0x430
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? tcp_recvmsg+0x1=
96/0x210
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? wake_affine+0x6=
2/0x1f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__wait_for_common=
+0x90/0x1d0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_schedule_=
timeout+0x10/0x10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0__flush_workqueue=
+0x13a/0x3f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd4_destroy_ses=
sion+0x1a4/0x240=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd4_proc_compou=
nd+0x44b/0x700 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd_dispatch+0x9=
4/0x1c0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0svc_process_commo=
n+0x2ec/0x660=20
> > > > > > [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_nfsd_disp=
atch+0x10/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_nfsd+0x10=
/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0svc_process+0x12d=
/0x170 [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0nfsd+0x84/0xb0 [n=
fsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0kthread+0xdd/0x10=
0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0? __pfx_kthread+0=
x10/0x10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0ret_from_fork+0x2=
9/0x50
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:10:08 2024] =C2=A0</TASK>
> > > > > >=20
> > > > > The above threads are trying to flush the workqueue, so that prob=
ably
> > > > > means that they are stuck waiting on a workqueue job to finish.
> > > > > > =C2=A0 =C2=A0The above is repeated a few times, and then this w=
arning is=20
> > > > > > also logged:
> > > > > > =C2=A0=C2=A0 [Mon Mar 11 14:12:04 2024] ------------[ cut here =
]------------
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:04 2024] WARNING: CPU: 39 PID: 8=
844 at=20
> > > > > > fs/nfsd/nfs4state.c:4919 nfsd_break_deleg_cb+0x170/0x190 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] Modules linked in: nfsv=
4=20
> > > > > > dns_resolver nfs fscache netfs rpcsec_gss_krb5 rpcrdma rdma_cm=
=20
> > > > > > iw_cm ib_cm ib_core binfmt_misc bonding tls rfkill nft_counter =
nft_ct
> > > > > > =C2=A0 =C2=A0nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_rej=
ect_inet=20
> > > > > > nf_reject_ipv4 nf_reject_ipv6 nft_reject nf_tables nfnetlink vf=
at=20
> > > > > > fat dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio l
> > > > > > =C2=A0 =C2=A0ibcrc32c dm_service_time dm_multipath intel_rapl_m=
sr=20
> > > > > > intel_rapl_common intel_uncore_frequency=20
> > > > > > intel_uncore_frequency_common isst_if_common skx_edac nfit=20
> > > > > > libnvdimm ipmi_ssif x86_pkg_temp
> > > > > > =C2=A0 =C2=A0_thermal intel_powerclamp coretemp kvm_intel kvm i=
rqbypass=20
> > > > > > dcdbas rapl intel_cstate mgag200 i2c_algo_bit drm_shmem_helper=
=20
> > > > > > dell_smbios drm_kms_helper dell_wmi_descriptor wmi_bmof intel_u
> > > > > > =C2=A0 =C2=A0ncore syscopyarea pcspkr sysfillrect mei_me sysimg=
blt acpi_ipmi=20
> > > > > > mei fb_sys_fops i2c_i801 ipmi_si intel_pch_thermal lpc_ich=20
> > > > > > ipmi_devintf i2c_smbus ipmi_msghandler joydev acpi_power_meter
> > > > > > =C2=A0 =C2=A0nfsd auth_rpcgss nfs_acl drm lockd grace fuse sunr=
pc ext4=20
> > > > > > mbcache jbd2 sd_mod sg lpfc
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nvmet_fc nvmet nv=
me_fc nvme_fabrics=20
> > > > > > crct10dif_pclmul ahci libahci crc32_pclmul nvme_core crc32c_int=
el=20
> > > > > > ixgbe megaraid_sas libata nvme_common ghash_clmulni_int
> > > > > > =C2=A0 =C2=A0el t10_pi wdat_wdt scsi_transport_fc mdio wmi dca =
dm_mirror=20
> > > > > > dm_region_hash dm_log dm_mod
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] CPU: 39 PID: 8844 Comm:=
 nfsd Not=20
> > > > > > tainted 5.14.0-419.el9.x86_64 #1
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] Hardware name: Dell Inc=
. PowerEdge=20
> > > > > > R740/00WGD1, BIOS 2.20.1 09/13/2023
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] RIP:=20
> > > > > > 0010:nfsd_break_deleg_cb+0x170/0x190 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] Code: a6 95 c5 f3 e9 ff=
 fe ff ff 48=20
> > > > > > 89 df be 01 00 00 00 e8 34 b5 13 f4 48 8d bb 98 00 00 00 e8 c8 =
f9=20
> > > > > > 00 00 84 c0 0f 85 2e ff ff ff <0f> 0b e9 27 ff ff ff be
> > > > > > =C2=A0 =C2=A002 00 00 00 48 89 df e8 0c b5 13 f4 e9 01
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] RSP: 0018:ffff9929e0bb7=
b80 EFLAGS:=20
> > > > > > 00010246
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] RAX: 0000000000000000 R=
BX:=20
> > > > > > ffff8ada51930900 RCX: 0000000000000024
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] RDX: ffff8ada519309c8 R=
SI:=20
> > > > > > ffff8ad582933c00 RDI: 0000000000002000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] RBP: ffff8ad46bf21574 R=
08:=20
> > > > > > ffff9929e0bb7b48 R09: 0000000000000000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] R10: ffff8aec859a2948 R=
11:=20
> > > > > > 0000000000000000 R12: ffff8ad6f497c360
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] R13: ffff8ad46bf21560 R=
14:=20
> > > > > > ffff8ae5942e0b10 R15: ffff8ad6f497c360
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] FS: =C2=A00000000000000=
000(0000)=20
> > > > > > GS:ffff8b031fcc0000(0000) knlGS:0000000000000000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] CS: =C2=A00010 DS: 0000=
 ES: 0000 CR0:=20
> > > > > > 0000000080050033
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] CR2: 00007fafe2060744 C=
R3:=20
> > > > > > 00000018e58de006 CR4: 00000000007706e0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] DR0: 0000000000000000 D=
R1:=20
> > > > > > 0000000000000000 DR2: 0000000000000000
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] DR3: 0000000000000000 D=
R6:=20
> > > > > > 00000000fffe0ff0 DR7: 0000000000000400
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] PKRU: 55555554
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] Call Trace:
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0<TASK>
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? show_trace_log_=
lvl+0x1c4/0x2df
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? show_trace_log_=
lvl+0x1c4/0x2df
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? __break_lease+0=
x16f/0x5f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? nfsd_break_dele=
g_cb+0x170/0x190=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? __warn+0x81/0x1=
10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? nfsd_break_dele=
g_cb+0x170/0x190=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? report_bug+0x10=
a/0x140
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? handle_bug+0x3c=
/0x70
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? exc_invalid_op+=
0x14/0x70
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? asm_exc_invalid=
_op+0x16/0x20
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? nfsd_break_dele=
g_cb+0x170/0x190=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0__break_lease+0x1=
6f/0x5f0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0?=20
> > > > > > nfsd_file_lookup_locked+0x117/0x160 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? list_lru_del+0x=
101/0x150
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd_file_do_acqu=
ire+0x790/0x830=20
> > > > > > [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfs4_get_vfs_file=
+0x315/0x3a0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd4_process_ope=
n2+0x430/0xa30 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? fh_verify+0x297=
/0x2f0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd4_open+0x3ce/=
0x4b0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd4_proc_compou=
nd+0x44b/0x700 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd_dispatch+0x9=
4/0x1c0 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0svc_process_commo=
n+0x2ec/0x660=20
> > > > > > [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? __pfx_nfsd_disp=
atch+0x10/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? __pfx_nfsd+0x10=
/0x10 [nfsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0svc_process+0x12d=
/0x170 [sunrpc]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0nfsd+0x84/0xb0 [n=
fsd]
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0kthread+0xdd/0x10=
0
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0? __pfx_kthread+0=
x10/0x10
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0ret_from_fork+0x2=
9/0x50
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] =C2=A0</TASK>
> > > > > > =C2=A0 =C2=A0[Mon Mar 11 14:12:05 2024] ---[ end trace 7a039e17=
443dc651 ]---
> > > > > This is probably this WARN in nfsd_break_one_deleg:
> > > > >=20
> > > > > WARN_ON_ONCE(!nfsd4_run_cb(&dp->dl_recall));
> > > > >=20
> > > > > It means that a delegation break callback to the client couldn't =
be
> > > > > queued to the workqueue, and so it didn't run.
> > > > >=20
> > > > > > Could this be the same issue as described=20
> > > > > > here:https://lore.kernel.org/linux-nfs/af0ec881-5ebf-4feb-98ae-=
3ed2a77f86f1@oracle.com/=20
> > > > > > ?
> > > > > Yes, most likely the same problem.
> > > > If I read that thread correctly, this issue was introduced between
> > > > 6.1.63 and 6.6.3? Is it possible the EL9 5.14.0-362.18.1.el9_3
> > > > backported these changes, or were we hitting some other bug with th=
at
> > > > version? It seems the 6.1.x kernel is not affected? If so, that=20
> > > > would be
> > > > the recommended kernel to run?
> > > Anything is possible. We have to identify the problem first.
> > > > > > As described in that thread, I've tried to obtain the requested=
=20
> > > > > > information.
> > > > > >=20
> > > > > > Is it possible this is the issue that was fixed by the patches=
=20
> > > > > > described=20
> > > > > > here?https://lore.kernel.org/linux-nfs/2024022054-cause-sufferi=
ng-eae8@gregkh/
> > > > > >=20
> > > > > Doubtful. Those are targeted toward a different set of issues.
> > > > >=20
> > > > > If you're willing, I do have some patches queued up for CentOS he=
re=20
> > > > > that
> > > > > fix some backchannel problems that could be related. I'm mainly=
=20
> > > > > waiting
> > > > > on Chuck to send these to Linus and then we'll likely merge them =
into
> > > > > CentOS soon afterward:
> > > > >=20
> > > > > https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-=
9/-/merge_requests/3689=20
> > > > >=20
> > > > >=20
> > > > If you can send me a patch file, I can rebuild the C9S kernel with =
that
> > > > patch and run it. It can take a while for the bug to trigger as I
> > > > believe it seems to be very workload dependent (we were running ver=
y
> > > > stable for months and now hit this bug every other week).
> > > >=20
> > > >=20
> > > It's probably simpler to just pull down the build artifacts for that =
MR.
> > > You have to drill down through the CI for it, but they are here:
> > >=20
> > > https://s3.amazonaws.com/arr-cki-prod-trusted-artifacts/index.html?pr=
efix=3Dtrusted-artifacts/1194300175/publish_x86_64/6278921877/artifacts/=
=20
> > >=20
> > >=20
> > > There's even a repo file you can install on the box to pull them down=
.
> >=20
> > We installed this kernel on the server 3 days ago. Today, a user=20
> > informed us that their screen was black after logging in. Similar to=
=20
> > other occurrences of this issue, the mount command on the client was=
=20
> > hung. But in contrast to the other times, there were no messages in=20
> > the logs kernel logs on the server. Even restarting the client does=20
> > not resolve the issue.


Ok, so you rebooted the client and it's still unable to mount? That
sounds like a server problem if so.

Are both client and server running the same kernel?

> >=20
> > Something still seems to be wrong on the server though. When I look at=
=20
> > the directories under /proc/fs/nfsd/clients, there's still a directory=
=20
> > for the specific client, even though it's no longer running:
> >=20
> > # cat 155/info
> > clientid: 0xc8edb7f65f4a9ad
> > address: "10.87.31.152:819"
> > status: confirmed
> > seconds from last renew: 33163
> > name: "Linux NFSv4.2 bersalis.esat.kuleuven.be"
> > minor version: 2
> > Implementation domain: "kernel.org"
> > Implementation name: "Linux 5.14.0-362.18.1.el9_3.0.1.x86_64 #1 SMP=20
> > PREEMPT_DYNAMIC Sun Feb 11 13:49:23 UTC 2024 x86_64"
> > Implementation time: [0, 0]
> > callback state: DOWN
> > callback address: 10.87.31.152:0
> >=20

If you just shut down the client, the server won't immediately purge its
record. In fact, assuming you're running the same kernel on the server,
it won't purge the client record until there is a conflicting request
for its state.


> The nfsdclnts command for this client shows the following delegations:
>=20
> # nfsdclnts -f 155/states -t all
> Inode number | Type=C2=A0=C2=A0 | Access | Deny | ip address=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | Filename
> 169346743=C2=A0=C2=A0=C2=A0 | open=C2=A0=C2=A0 | r-=C2=A0=C2=A0=C2=A0=C2=
=A0 | --=C2=A0=C2=A0 | 10.87.31.152:819=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=20
> disconnected dentry
> 169346743=C2=A0=C2=A0=C2=A0 | deleg=C2=A0 | r=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 |=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 10.87.31.152:819=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0 |=20
> disconnected dentry
> 169346746=C2=A0=C2=A0=C2=A0 | open=C2=A0=C2=A0 | r-=C2=A0=C2=A0=C2=A0=C2=
=A0 | --=C2=A0=C2=A0 | 10.87.31.152:819=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=20
> disconnected dentry
> 169346746=C2=A0=C2=A0=C2=A0 | deleg=C2=A0 | r=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 |=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 10.87.31.152:819=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0 |=20
> disconnected dentry
>=20
> I see a lot of recent patches regarding directory delegations. Could=20
> this be related to this?
>=20
> Will a 5.14.0-362.18.1.el9_3.0.1 kernel try to use a directory delegation=
?
>=20
>=20

No. Directory delegations are a new feature that's still under
development. They use some of the same machinery as file delegations,
but they wouldn't be a factor here.

>=20
> >=20
> > The system seems to have identified that the client is no longer=20
> > reachable, but the client entry does not go away. When a mount was=20
> > hanging on the client, there would be two directories in clients for=
=20
> > the same client. Killing the mount command clears up the second entry.
> >=20
> > Even after running conntrack -D on the server to remove the tcp=20
> > connection from the conntrack table, the entry doesn't go away and the=
=20
> > client still can not mount anything from the server.
> >=20
> > A tcpdump on the client while a mount was running logged the following=
=20
> > messages over and over again:
> >=20
> > request:
> >=20
> > Frame 1: 378 bytes on wire (3024 bits), 378 bytes captured (3024 bits)
> > Ethernet II, Src: HP_19:7d:4b (e0:73:e7:19:7d:4b), Dst:=20
> > ArubaaHe_f9:8e:00 (88:3a:30:f9:8e:00)
> > Internet Protocol Version 4, Src: 10.87.31.152, Dst: 10.86.18.14
> > Transmission Control Protocol, Src Port: 932, Dst Port: 2049, Seq: 1,=
=20
> > Ack: 1, Len: 312
> > Remote Procedure Call, Type:Call XID:0x1d3220c4
> > Network File System
> > =C2=A0=C2=A0=C2=A0 [Program Version: 4]
> > =C2=A0=C2=A0=C2=A0 [V4 Procedure: COMPOUND (1)]
> > =C2=A0=C2=A0=C2=A0 GSS Data, Ops(1): CREATE_SESSION
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Length: 152
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS Sequence Number: 76
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Tag: <EMPTY>
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 minorversion: 2
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Operations (count: 1): CREAT=
E_SESSION
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [Main Opcode: CREATE_SESSION=
 (43)]
> > =C2=A0=C2=A0=C2=A0 GSS Checksum:=20
> > 00000028040404ffffffffff000000002c19055f1f8d442d594c13849628affc2797cbb=
2=E2=80=A6
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS Token Length: 40
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS-API Generic Security Ser=
vice Application Program Interface
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 krb5=
_blob:=20
> > 040404ffffffffff000000002c19055f1f8d442d594c13849628affc2797cbb23fa080b=
0=E2=80=A6
> >=20
> > response:
> >=20
> > Frame 2: 206 bytes on wire (1648 bits), 206 bytes captured (1648 bits)
> > Ethernet II, Src: ArubaaHe_f9:8e:00 (88:3a:30:f9:8e:00), Dst:=20
> > HP_19:7d:4b (e0:73:e7:19:7d:4b)
> > Internet Protocol Version 4, Src: 10.86.18.14, Dst: 10.87.31.152
> > Transmission Control Protocol, Src Port: 2049, Dst Port: 932, Seq: 1,=
=20
> > Ack: 313, Len: 140
> > Remote Procedure Call, Type:Reply XID:0x1d3220c4
> > Network File System
> > =C2=A0=C2=A0=C2=A0 [Program Version: 4]
> > =C2=A0=C2=A0=C2=A0 [V4 Procedure: COMPOUND (1)]
> > =C2=A0=C2=A0=C2=A0 GSS Data, Ops(1): CREATE_SESSION(NFS4ERR_DELAY)
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Length: 24
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS Sequence Number: 76
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Status: NFS4ERR_DELAY (10008=
)
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Tag: <EMPTY>
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Operations (count: 1)
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [Main Opcode: CREATE_SESSION=
 (43)]
> > =C2=A0=C2=A0=C2=A0 GSS Checksum:=20
> > 00000028040405ffffffffff000000000aa742d0798deaad1a8aa2d7c3a91bf4f627422=
2=E2=80=A6
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS Token Length: 40
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 GSS-API Generic Security Ser=
vice Application Program Interface
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 krb5=
_blob:=20
> > 040405ffffffffff000000000aa742d0798deaad1a8aa2d7c3a91bf4f627422226d7492=
3=E2=80=A6
> >=20
> > I was hoping that giving the client a different IP address would=20
> > resolve the issue for this client, but it didn't. Even though the=20
> > client had a new IP address (hostname was kept the same), it failed to=
=20
> > mount anything from the server.
> >=20

Changing the IP address won't help. The client is probably using the
same long-form client id as before, so the server still identifies the
client even with the address change.

Unfortunately, the cause of an NFS4ERR_DELAY error is tough to guess.
The client is expected to back off and retry, so if the server keeps
returning that repeatedly, then a hung mount command is expected.

The question is why the server would keep returning DELAY. A lot of
different problems ranging from memory allocation issues to protocol
problems can result in that error. You may want to check the NFS server
and see if anything was logged there.

This is on a CREATE_SESSION call, so I wonder if the record held by the
(courteous) server is somehow blocking the attempt to reestablish the
session?

Do you have a way to reproduce this? Since this is a centos kernel, you
could follow the page here to open a bug:

    https://wiki.centos.org/ReportBugs.html


> > I created another dump of the workqueues and worker pools on the server=
:
> >=20
> > [Mon Mar 18 14:59:33 2024] Showing busy workqueues and worker pools:
> > [Mon Mar 18 14:59:33 2024] workqueue events: flags=3D0x0
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0pwq 54: cpus=3D27 node=3D1 flags=
=3D0x0 nice=3D0=20
> > active=3D1/256 refcnt=3D2
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0=C2=A0=C2=A0pending: drm_fb_help=
er_damage_work=20
> > [drm_kms_helper]
> > [Mon Mar 18 14:59:33 2024] workqueue events_power_efficient: flags=3D0x=
80
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0pwq 54: cpus=3D27 node=3D1 flags=
=3D0x0 nice=3D0=20
> > active=3D1/256 refcnt=3D2
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0=C2=A0=C2=A0pending: fb_flashcur=
sor
> > [Mon Mar 18 14:59:33 2024] workqueue mm_percpu_wq: flags=3D0x8
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0pwq 54: cpus=3D27 node=3D1 flags=
=3D0x0 nice=3D0=20
> > active=3D1/256 refcnt=3D3
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0=C2=A0=C2=A0pending: lru_add_dra=
in_per_cpu BAR(362)
> > [Mon Mar 18 14:59:33 2024] workqueue kblockd: flags=3D0x18
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0pwq 55: cpus=3D27 node=3D1 flags=
=3D0x0 nice=3D-20=20
> > active=3D1/256 refcnt=3D2
> > [Mon Mar 18 14:59:33 2024] =C2=A0=C2=A0=C2=A0=C2=A0pending: blk_mq_time=
out_work
> >=20
> >=20
> > In contrast to last time, it doesn't show anything regarding nfs this=
=20
> > time.
> >=20
> > I also tried the suggestion from Dai Ngo (echo 3 >=20
> > /proc/sys/vm/drop_caches), but that didn't seem to make any difference.
> >=20
> > We haven't restarted the server yet as it seems the impact seems to=20
> > affect fewer clients that before. Is there anything we can run on the=
=20
> > server to further debug this?
> >=20
> > In the past, the issue seemed to deteriorate rapidly and resulted in=
=20
> > issues for almost all clients after about 20 minutes. This time the=20
> > impact seems to be less, but it's not gone.
> >=20
> > How can we force the NFS server to forget about a specific client? I=
=20
> > haven't tried to restart the nfs service yet as I'm afraid it will=20
> > fail to stop as before.
> >=20

Not with that kernel. There are some new administrative interfaces that
might allow that in the future, but they were just merged upstream and
aren't in that kernel.

--
Jeff Layton <jlayton@kernel.org>