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Message-ID: <afe6c2a2-443d-465e-8e47-b3fe24050cba@esat.kuleuven.be>
Date: Tue, 19 Mar 2024 11:58:17 +0100
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: nfsd hangs and nfsd_break_deleg_cb+0x170/0x190 warning
Content-Language: en-US
To: Jeff Layton <jlayton@kernel.org>, Linux Nfs <linux-nfs@vger.kernel.org>
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>
 <7d244882d769e377b06f39234bd5ee7dddb72a55.camel@kernel.org>
 <c7dbc796-7e7d-4041-ac71-eea02a701b12@esat.kuleuven.be>
 <caeb133cc80c730e84f97732581d8d59def342b8.camel@kernel.org>
From: Rik Theys <Rik.Theys@esat.kuleuven.be>
In-Reply-To: <caeb133cc80c730e84f97732581d8d59def342b8.camel@kernel.org>
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Hi,

On 3/19/24 11:39, Jeff Layton wrote:
> On Tue, 2024-03-19 at 08:58 +0100, Rik Theys wrote:
>> Hi,
>>
>> On 3/18/24 22:54, Jeff Layton wrote:
>>> On Mon, 2024-03-18 at 22:15 +0100, Rik Theys wrote:
>>>> Hi,
>>>>
>>>> On 3/18/24 21:21, Rik Theys wrote:
>>>>> Hi Jeff,
>>>>>
>>>>> On 3/12/24 13:47, Jeff Layton wrote:
>>>>>> On Tue, 2024-03-12 at 13:24 +0100, Rik Theys wrote:
>>>>>>> Hi Jeff,
>>>>>>>
>>>>>>> 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
>>>>>>>>> logged hung nfsd tasks. The initial effect was that some clients
>>>>>>>>> could no longer access the NFS server. This got worse and worse
>>>>>>>>> (probably as more nfsd threads got blocked) and we had to restart
>>>>>>>>> the server. Restarting the server also failed as the NFS server
>>>>>>>>> service could no longer be stopped.
>>>>>>>>>
>>>>>>>>> The initial kernel we noticed this behavior on was
>>>>>>>>> kernel-5.14.0-362.18.1.el9_3.x86_64. Since then we've installed
>>>>>>>>> kernel-5.14.0-419.el9.x86_64 from CentOS Stream 9. The same issue
>>>>>>>>> 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.
>>>>>>
>>>>>> 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.
>>>>>>
>>>>>>>>> [Mon Mar 11 14:10:08 2024]       Not tainted 5.14.0-419.el9.x86_64 #1
>>>>>>>>>      [Mon Mar 11 14:10:08 2024] "echo 0 >
>>>>>>>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]task:nfsd             state:D stack:0
>>>>>>>>>       pid:8865  ppid:2      flags:0x00004000
>>>>>>>>>      [Mon Mar 11 14:10:08 2024] Call Trace:
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  <TASK>
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __schedule+0x21b/0x550
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  schedule+0x2d/0x70
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  schedule_timeout+0x11f/0x160
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? select_idle_sibling+0x28/0x430
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? wake_affine+0x62/0x1f0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __wait_for_common+0x90/0x1d0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_schedule_timeout+0x10/0x10
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __flush_workqueue+0x13a/0x3f0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd4_shutdown_callback+0x49/0x120
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? nfsd4_cld_remove+0x54/0x1d0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ?
>>>>>>>>> nfsd4_return_all_client_layouts+0xc4/0xf0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? nfsd4_shutdown_copy+0x68/0xc0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __destroy_client+0x1f3/0x290 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd4_exchange_id+0x75f/0x770 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? nfsd4_decode_opaque+0x3a/0x90 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd4_proc_compound+0x44b/0x700 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd_dispatch+0x94/0x1c0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  svc_process_common+0x2ec/0x660
>>>>>>>>> [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_nfsd+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  svc_process+0x12d/0x170 [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd+0x84/0xb0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  kthread+0xdd/0x100
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_kthread+0x10/0x10
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ret_from_fork+0x29/0x50
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  </TASK>
>>>>>>>>>      [Mon Mar 11 14:10:08 2024] INFO: task nfsd:8866 blocked for
>>>>>>>>> more than 122 seconds.
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]       Not tainted
>>>>>>>>> 5.14.0-419.el9.x86_64 #1
>>>>>>>>>      [Mon Mar 11 14:10:08 2024] "echo 0 >
>>>>>>>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]task:nfsd             state:D stack:0
>>>>>>>>>       pid:8866  ppid:2      flags:0x00004000
>>>>>>>>>      [Mon Mar 11 14:10:08 2024] Call Trace:
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  <TASK>
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __schedule+0x21b/0x550
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  schedule+0x2d/0x70
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  schedule_timeout+0x11f/0x160
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? select_idle_sibling+0x28/0x430
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? tcp_recvmsg+0x196/0x210
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? wake_affine+0x62/0x1f0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __wait_for_common+0x90/0x1d0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_schedule_timeout+0x10/0x10
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  __flush_workqueue+0x13a/0x3f0
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd4_destroy_session+0x1a4/0x240
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd4_proc_compound+0x44b/0x700 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd_dispatch+0x94/0x1c0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  svc_process_common+0x2ec/0x660
>>>>>>>>> [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_nfsd+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  svc_process+0x12d/0x170 [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  nfsd+0x84/0xb0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  kthread+0xdd/0x100
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ? __pfx_kthread+0x10/0x10
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  ret_from_fork+0x29/0x50
>>>>>>>>>      [Mon Mar 11 14:10:08 2024]  </TASK>
>>>>>>>>>
>>>>>>>> The above threads are trying to flush the workqueue, so that probably
>>>>>>>> means that they are stuck waiting on a workqueue job to finish.
>>>>>>>>>      The above is repeated a few times, and then this warning is
>>>>>>>>> also logged:
>>>>>>>>>      [Mon Mar 11 14:12:04 2024] ------------[ cut here ]------------
>>>>>>>>>      [Mon Mar 11 14:12:04 2024] WARNING: CPU: 39 PID: 8844 at
>>>>>>>>> fs/nfsd/nfs4state.c:4919 nfsd_break_deleg_cb+0x170/0x190 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] Modules linked in: nfsv4
>>>>>>>>> dns_resolver nfs fscache netfs rpcsec_gss_krb5 rpcrdma rdma_cm
>>>>>>>>> iw_cm ib_cm ib_core binfmt_misc bonding tls rfkill nft_counter nft_ct
>>>>>>>>>      nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_reject_inet
>>>>>>>>> nf_reject_ipv4 nf_reject_ipv6 nft_reject nf_tables nfnetlink vfat
>>>>>>>>> fat dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio l
>>>>>>>>>      ibcrc32c dm_service_time dm_multipath intel_rapl_msr
>>>>>>>>> intel_rapl_common intel_uncore_frequency
>>>>>>>>> intel_uncore_frequency_common isst_if_common skx_edac nfit
>>>>>>>>> libnvdimm ipmi_ssif x86_pkg_temp
>>>>>>>>>      _thermal intel_powerclamp coretemp kvm_intel kvm irqbypass
>>>>>>>>> dcdbas rapl intel_cstate mgag200 i2c_algo_bit drm_shmem_helper
>>>>>>>>> dell_smbios drm_kms_helper dell_wmi_descriptor wmi_bmof intel_u
>>>>>>>>>      ncore syscopyarea pcspkr sysfillrect mei_me sysimgblt acpi_ipmi
>>>>>>>>> mei fb_sys_fops i2c_i801 ipmi_si intel_pch_thermal lpc_ich
>>>>>>>>> ipmi_devintf i2c_smbus ipmi_msghandler joydev acpi_power_meter
>>>>>>>>>      nfsd auth_rpcgss nfs_acl drm lockd grace fuse sunrpc ext4
>>>>>>>>> mbcache jbd2 sd_mod sg lpfc
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nvmet_fc nvmet nvme_fc nvme_fabrics
>>>>>>>>> crct10dif_pclmul ahci libahci crc32_pclmul nvme_core crc32c_intel
>>>>>>>>> ixgbe megaraid_sas libata nvme_common ghash_clmulni_int
>>>>>>>>>      el t10_pi wdat_wdt scsi_transport_fc mdio wmi dca dm_mirror
>>>>>>>>> dm_region_hash dm_log dm_mod
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] CPU: 39 PID: 8844 Comm: nfsd Not
>>>>>>>>> tainted 5.14.0-419.el9.x86_64 #1
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] Hardware name: Dell Inc. PowerEdge
>>>>>>>>> R740/00WGD1, BIOS 2.20.1 09/13/2023
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] RIP:
>>>>>>>>> 0010:nfsd_break_deleg_cb+0x170/0x190 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] Code: a6 95 c5 f3 e9 ff fe ff ff 48
>>>>>>>>> 89 df be 01 00 00 00 e8 34 b5 13 f4 48 8d bb 98 00 00 00 e8 c8 f9
>>>>>>>>> 00 00 84 c0 0f 85 2e ff ff ff <0f> 0b e9 27 ff ff ff be
>>>>>>>>>      02 00 00 00 48 89 df e8 0c b5 13 f4 e9 01
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] RSP: 0018:ffff9929e0bb7b80 EFLAGS:
>>>>>>>>> 00010246
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] RAX: 0000000000000000 RBX:
>>>>>>>>> ffff8ada51930900 RCX: 0000000000000024
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] RDX: ffff8ada519309c8 RSI:
>>>>>>>>> ffff8ad582933c00 RDI: 0000000000002000
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] RBP: ffff8ad46bf21574 R08:
>>>>>>>>> ffff9929e0bb7b48 R09: 0000000000000000
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] R10: ffff8aec859a2948 R11:
>>>>>>>>> 0000000000000000 R12: ffff8ad6f497c360
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] R13: ffff8ad46bf21560 R14:
>>>>>>>>> ffff8ae5942e0b10 R15: ffff8ad6f497c360
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] FS:  0000000000000000(0000)
>>>>>>>>> GS:ffff8b031fcc0000(0000) knlGS:0000000000000000
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] CS:  0010 DS: 0000 ES: 0000 CR0:
>>>>>>>>> 0000000080050033
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] CR2: 00007fafe2060744 CR3:
>>>>>>>>> 00000018e58de006 CR4: 00000000007706e0
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] DR0: 0000000000000000 DR1:
>>>>>>>>> 0000000000000000 DR2: 0000000000000000
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] DR3: 0000000000000000 DR6:
>>>>>>>>> 00000000fffe0ff0 DR7: 0000000000000400
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] PKRU: 55555554
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] Call Trace:
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  <TASK>
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? show_trace_log_lvl+0x1c4/0x2df
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? show_trace_log_lvl+0x1c4/0x2df
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? __break_lease+0x16f/0x5f0
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? nfsd_break_deleg_cb+0x170/0x190
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? __warn+0x81/0x110
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? nfsd_break_deleg_cb+0x170/0x190
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? report_bug+0x10a/0x140
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? handle_bug+0x3c/0x70
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? exc_invalid_op+0x14/0x70
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? asm_exc_invalid_op+0x16/0x20
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? nfsd_break_deleg_cb+0x170/0x190
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  __break_lease+0x16f/0x5f0
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ?
>>>>>>>>> nfsd_file_lookup_locked+0x117/0x160 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? list_lru_del+0x101/0x150
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd_file_do_acquire+0x790/0x830
>>>>>>>>> [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfs4_get_vfs_file+0x315/0x3a0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd4_process_open2+0x430/0xa30 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? fh_verify+0x297/0x2f0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd4_open+0x3ce/0x4b0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd4_proc_compound+0x44b/0x700 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd_dispatch+0x94/0x1c0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  svc_process_common+0x2ec/0x660
>>>>>>>>> [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? __pfx_nfsd+0x10/0x10 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  svc_process+0x12d/0x170 [sunrpc]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  nfsd+0x84/0xb0 [nfsd]
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  kthread+0xdd/0x100
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ? __pfx_kthread+0x10/0x10
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  ret_from_fork+0x29/0x50
>>>>>>>>>      [Mon Mar 11 14:12:05 2024]  </TASK>
>>>>>>>>>      [Mon Mar 11 14:12:05 2024] ---[ end trace 7a039e17443dc651 ]---
>>>>>>>> This is probably this WARN in nfsd_break_one_deleg:
>>>>>>>>
>>>>>>>> WARN_ON_ONCE(!nfsd4_run_cb(&dp->dl_recall));
>>>>>>>>
>>>>>>>> It means that a delegation break callback to the client couldn't be
>>>>>>>> queued to the workqueue, and so it didn't run.
>>>>>>>>
>>>>>>>>> Could this be the same issue as described
>>>>>>>>> here:https://lore.kernel.org/linux-nfs/af0ec881-5ebf-4feb-98ae-3ed2a77f86f1@oracle.com/
>>>>>>>>> ?
>>>>>>>> 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 that
>>>>>>> version? It seems the 6.1.x kernel is not affected? If so, that
>>>>>>> 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
>>>>>>>>> information.
>>>>>>>>>
>>>>>>>>> Is it possible this is the issue that was fixed by the patches
>>>>>>>>> described
>>>>>>>>> here?https://lore.kernel.org/linux-nfs/2024022054-cause-suffering-eae8@gregkh/
>>>>>>>>>
>>>>>>>> Doubtful. Those are targeted toward a different set of issues.
>>>>>>>>
>>>>>>>> If you're willing, I do have some patches queued up for CentOS here
>>>>>>>> that
>>>>>>>> fix some backchannel problems that could be related. I'm mainly
>>>>>>>> waiting
>>>>>>>> on Chuck to send these to Linus and then we'll likely merge them into
>>>>>>>> CentOS soon afterward:
>>>>>>>>
>>>>>>>> https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/3689
>>>>>>>>
>>>>>>>>
>>>>>>> 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 very
>>>>>>> stable for months and now hit this bug every other week).
>>>>>>>
>>>>>>>
>>>>>> 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:
>>>>>>
>>>>>> https://s3.amazonaws.com/arr-cki-prod-trusted-artifacts/index.html?prefix=trusted-artifacts/1194300175/publish_x86_64/6278921877/artifacts/
>>>>>>
>>>>>>
>>>>>> There's even a repo file you can install on the box to pull them down.
>>>>> We installed this kernel on the server 3 days ago. Today, a user
>>>>> informed us that their screen was black after logging in. Similar to
>>>>> other occurrences of this issue, the mount command on the client was
>>>>> hung. But in contrast to the other times, there were no messages in
>>>>> the logs kernel logs on the server. Even restarting the client does
>>>>> 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?
>> No, the server runs 5.14.0-427.3689_1194299994.el9 and the client
>> 5.14.0-362.18.1.el9_3.
> Ok.
>
>>>>> Something still seems to be wrong on the server though. When I look at
>>>>> the directories under /proc/fs/nfsd/clients, there's still a directory
>>>>> for the specific client, even though it's no longer running:
>>>>>
>>>>> # 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
>>>>> 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
>>>>>
>>> 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.
>> Is there a way to force such a conflicting request (to get the client
>> record to purge)?
>  From the server or a different client, you can try opening the inodes
> that the stuck client is holding open. If you open them for write, that
> may trigger the server to kick out the old client record.
>
> The problem is that they are disconnected dentries, so finding them to
> open via path may be difficult...

I've located the file that matches one of these inodes. When I go to the

location of the file on another NFS client and touch the file, the touch 
command

just hangs.

So I assume the server is trying to recall the delegation from the 
dis-functional client?

When I run tcpdump on the dis-functional client, I see the 
CREATE_SESSION / NFS4ERR_DELAY messages, but nothing to indicate the 
server wants to revoke a delegation.

The entry for the dis-functional client is not removed on the server.

I there anything else I can do to provide more information about this 
situation?

Regards,

Rik


>>>> The nfsdclnts command for this client shows the following delegations:
>>>>
>>>> # nfsdclnts -f 155/states -t all
>>>> Inode number | Type   | Access | Deny | ip address            | Filename
>>>> 169346743    | open   | r-     | --   | 10.87.31.152:819      |
>>>> disconnected dentry
>>>> 169346743    | deleg  | r      |      | 10.87.31.152:819      |
>>>> disconnected dentry
>>>> 169346746    | open   | r-     | --   | 10.87.31.152:819      |
>>>> disconnected dentry
>>>> 169346746    | deleg  | r      |      | 10.87.31.152:819      |
>>>> disconnected dentry
>>>>
>>>> I see a lot of recent patches regarding directory delegations. Could
>>>> this be related to this?
>>>>
>>>> Will a 5.14.0-362.18.1.el9_3.0.1 kernel try to use a directory delegation?
>>>>
>>>>
>>> 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.
>>>
>>>>> The system seems to have identified that the client is no longer
>>>>> reachable, but the client entry does not go away. When a mount was
>>>>> hanging on the client, there would be two directories in clients for
>>>>> the same client. Killing the mount command clears up the second entry.
>>>>>
>>>>> Even after running conntrack -D on the server to remove the tcp
>>>>> connection from the conntrack table, the entry doesn't go away and the
>>>>> client still can not mount anything from the server.
>>>>>
>>>>> A tcpdump on the client while a mount was running logged the following
>>>>> messages over and over again:
>>>>>
>>>>> request:
>>>>>
>>>>> 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:
>>>>> 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,
>>>>> Ack: 1, Len: 312
>>>>> Remote Procedure Call, Type:Call XID:0x1d3220c4
>>>>> Network File System
>>>>>       [Program Version: 4]
>>>>>       [V4 Procedure: COMPOUND (1)]
>>>>>       GSS Data, Ops(1): CREATE_SESSION
>>>>>           Length: 152
>>>>>           GSS Sequence Number: 76
>>>>>           Tag: <EMPTY>
>>>>>           minorversion: 2
>>>>>           Operations (count: 1): CREATE_SESSION
>>>>>           [Main Opcode: CREATE_SESSION (43)]
>>>>>       GSS Checksum:
>>>>> 00000028040404ffffffffff000000002c19055f1f8d442d594c13849628affc2797cbb2…
>>>>>           GSS Token Length: 40
>>>>>           GSS-API Generic Security Service Application Program Interface
>>>>>               krb5_blob:
>>>>> 040404ffffffffff000000002c19055f1f8d442d594c13849628affc2797cbb23fa080b0…
>>>>>
>>>>> response:
>>>>>
>>>>> 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:
>>>>> 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,
>>>>> Ack: 313, Len: 140
>>>>> Remote Procedure Call, Type:Reply XID:0x1d3220c4
>>>>> Network File System
>>>>>       [Program Version: 4]
>>>>>       [V4 Procedure: COMPOUND (1)]
>>>>>       GSS Data, Ops(1): CREATE_SESSION(NFS4ERR_DELAY)
>>>>>           Length: 24
>>>>>           GSS Sequence Number: 76
>>>>>           Status: NFS4ERR_DELAY (10008)
>>>>>           Tag: <EMPTY>
>>>>>           Operations (count: 1)
>>>>>           [Main Opcode: CREATE_SESSION (43)]
>>>>>       GSS Checksum:
>>>>> 00000028040405ffffffffff000000000aa742d0798deaad1a8aa2d7c3a91bf4f6274222…
>>>>>           GSS Token Length: 40
>>>>>           GSS-API Generic Security Service Application Program Interface
>>>>>               krb5_blob:
>>>>> 040405ffffffffff000000000aa742d0798deaad1a8aa2d7c3a91bf4f627422226d74923…
>>>>>
>>>>> I was hoping that giving the client a different IP address would
>>>>> resolve the issue for this client, but it didn't. Even though the
>>>>> client had a new IP address (hostname was kept the same), it failed to
>>>>> mount anything from the server.
>>>>>
>>> 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.
>> How is the client id determined? Will changing the hostname of the
>> client trigger a change of the client id?
> In the client record you showed a bit above, there is a "name" field:
>
>      name: "Linux NFSv4.2 bersalis.esat.kuleuven.be"
>
> That's the string the server uses to uniquely identify the client. So
> yes, changing the hostname should change that string.
>
>>> 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.
>> There are no messages in the system logs that indicate any sort of
>> memory issue. We also increased the min_kbytes_free sysctl to 2G on the
>> server before we restarted it with the newer kernel.
> Ok, I didn't expect to see anything like that, but it was a possibility.
>
>>> 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:
>> Unfortunately we haven't found a reliable way to reproduce it. But we do
>> seem to trigger it more and more lately.
>>
>>
> Bummer, ok. Let us know if you figure out a way to reproduce it.
>
>>>       https://wiki.centos.org/ReportBugs.html
>>>
>>>
>>>>> I created another dump of the workqueues and worker pools on the server:
>>>>>
>>>>> [Mon Mar 18 14:59:33 2024] Showing busy workqueues and worker pools:
>>>>> [Mon Mar 18 14:59:33 2024] workqueue events: flags=0x0
>>>>> [Mon Mar 18 14:59:33 2024]   pwq 54: cpus=27 node=1 flags=0x0 nice=0
>>>>> active=1/256 refcnt=2
>>>>> [Mon Mar 18 14:59:33 2024]     pending: drm_fb_helper_damage_work
>>>>> [drm_kms_helper]
>>>>> [Mon Mar 18 14:59:33 2024] workqueue events_power_efficient: flags=0x80
>>>>> [Mon Mar 18 14:59:33 2024]   pwq 54: cpus=27 node=1 flags=0x0 nice=0
>>>>> active=1/256 refcnt=2
>>>>> [Mon Mar 18 14:59:33 2024]     pending: fb_flashcursor
>>>>> [Mon Mar 18 14:59:33 2024] workqueue mm_percpu_wq: flags=0x8
>>>>> [Mon Mar 18 14:59:33 2024]   pwq 54: cpus=27 node=1 flags=0x0 nice=0
>>>>> active=1/256 refcnt=3
>>>>> [Mon Mar 18 14:59:33 2024]     pending: lru_add_drain_per_cpu BAR(362)
>>>>> [Mon Mar 18 14:59:33 2024] workqueue kblockd: flags=0x18
>>>>> [Mon Mar 18 14:59:33 2024]   pwq 55: cpus=27 node=1 flags=0x0 nice=-20
>>>>> active=1/256 refcnt=2
>>>>> [Mon Mar 18 14:59:33 2024]     pending: blk_mq_timeout_work
>>>>>
>>>>>
>>>>> In contrast to last time, it doesn't show anything regarding nfs this
>>>>> time.
>>>>>
>>>>> I also tried the suggestion from Dai Ngo (echo 3 >
>>>>> /proc/sys/vm/drop_caches), but that didn't seem to make any difference.
>>>>>
>>>>> We haven't restarted the server yet as it seems the impact seems to
>>>>> affect fewer clients that before. Is there anything we can run on the
>>>>> server to further debug this?
>>>>>
>>>>> In the past, the issue seemed to deteriorate rapidly and resulted in
>>>>> issues for almost all clients after about 20 minutes. This time the
>>>>> impact seems to be less, but it's not gone.
>>>>>
>>>>> How can we force the NFS server to forget about a specific client? I
>>>>> haven't tried to restart the nfs service yet as I'm afraid it will
>>>>> fail to stop as before.
>>>>>
>>> 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>

-- 
Rik Theys
System Engineer
KU Leuven - Dept. Elektrotechniek (ESAT)
Kasteelpark Arenberg 10 bus 2440  - B-3001 Leuven-Heverlee
+32(0)16/32.11.07
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<<Any errors in spelling, tact or fact are transmission errors>>