Re: nfsd hangs and nfsd_break_deleg_cb+0x170/0x190 warning

[Rik Theys <Rik.Theys@esat.kuleuven.be>]

Hi,

On 3/19/24 18:09, Dai Ngo wrote:
>
> On 3/19/24 12:58 AM, 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://urldefense.com/v3/__https://lore.kernel.org/linux-nfs/af0ec881-5ebf-4feb-98ae-3ed2a77f86f1@oracle.com/__;!!ACWV5N9M2RV99hQ!LV3yWeoSOhNAkRHkxFCH2tlm0iNFVD78mxnSLyP6lrX7yBVeA2TOJ4nv6oZsqLwP4kW56CMpDWhkjjwSkdBV9En7$ 
>>>>>>>>> ?
>>>>>>>> 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://urldefense.com/v3/__https://lore.kernel.org/linux-nfs/2024022054-cause-suffering-eae8@gregkh/__;!!ACWV5N9M2RV99hQ!LV3yWeoSOhNAkRHkxFCH2tlm0iNFVD78mxnSLyP6lrX7yBVeA2TOJ4nv6oZsqLwP4kW56CMpDWhkjjwSkedtUP09$ 
>>>>>>>>>
>>>>>>>> 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://urldefense.com/v3/__https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/3689__;!!ACWV5N9M2RV99hQ!LV3yWeoSOhNAkRHkxFCH2tlm0iNFVD78mxnSLyP6lrX7yBVeA2TOJ4nv6oZsqLwP4kW56CMpDWhkjjwSkdvDn8y7$ 
>>>>>>>>
>>>>>>>>
>>>>>>> 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://urldefense.com/v3/__https://s3.amazonaws.com/arr-cki-prod-trusted-artifacts/index.html?prefix=trusted-artifacts*1194300175*publish_x86_64*6278921877*artifacts*__;Ly8vLy8!!ACWV5N9M2RV99hQ!LV3yWeoSOhNAkRHkxFCH2tlm0iNFVD78mxnSLyP6lrX7yBVeA2TOJ4nv6oZsqLwP4kW56CMpDWhkjjwSkaP5eW8V$ 
>>>>>>
>>>>>>
>>>>>> 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.
>>>
>>>>> 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)?
>
> Try:
>
> # echo "expire" > /proc/fs/nfsd/clients/155/ctl

I've tried that. The command hangs and can not be interrupted with ctrl-c.

I've now also noticed in the dmesg output that the kernel issued the 
following WARNING a few hours ago. It wasn't directly triggered by the 
echo command above, but seems to have been triggered a few hours ago 
(probably when another client started to have the same problem as more 
clients are experiencing issues now).

[Tue Mar 19 14:53:44 2024] ------------[ cut here ]------------
[Tue Mar 19 14:53:44 2024] WARNING: CPU: 44 PID: 5843 at 
fs/nfsd/nfs4state.c:4920 nfsd_break_deleg_cb+0x170/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024] Modules linked in: nf_conntrack_netlink nfsv4 
dns_resolver nfs fscache netfs binfmt_misc xsk_diag rpcsec_gss_krb5 
rpcrdma rdma_cm iw_cm ib_cm ib_core 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 libcrc32c 
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 x86_pkg_temp_thermal intel_powerclamp coretemp 
kvm_intel kvm dcdbas irqbypass ipmi_ssif rapl intel_cstate mgag200 
i2c_algo_bit drm_shmem_helper drm_kms_helper dell_smbios syscopyarea 
intel_uncore sysfillrect wmi_bmof dell_wmi_descriptor pcspkr sysimgblt 
fb_sys_fops mei_me i2c_i801 mei intel_pch_thermal acpi_ipmi i2c_smbus 
lpc_ich ipmi_si ipmi_devintf ipmi_msghandler joydev acpi_power_meter 
nfsd nfs_acl lockd auth_rpcgss grace drm fuse sunrpc ext4
[Tue Mar 19 14:53:44 2024]  mbcache jbd2 sd_mod sg lpfc nvmet_fc nvmet 
nvme_fc nvme_fabrics crct10dif_pclmul crc32_pclmul nvme_core ixgbe 
crc32c_intel ahci libahci nvme_common megaraid_sas t10_pi 
ghash_clmulni_intel wdat_wdt libata scsi_transport_fc mdio dca wmi 
dm_mirror dm_region_hash dm_log dm_mod
[Tue Mar 19 14:53:44 2024] CPU: 44 PID: 5843 Comm: nfsd Not tainted 
5.14.0-427.3689_1194299994.el9.x86_64 #1
[Tue Mar 19 14:53:44 2024] Hardware name: Dell Inc. PowerEdge 
R740/00WGD1, BIOS 2.20.1 09/13/2023
[Tue Mar 19 14:53:44 2024] RIP: 0010:nfsd_break_deleg_cb+0x170/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024] Code: 76 76 cd de e9 ff fe ff ff 48 89 df be 
01 00 00 00 e8 34 a1 1b df 48 8d bb 98 00 00 00 e8 a8 fe 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 a1 
1b df e9 01
[Tue Mar 19 14:53:44 2024] RSP: 0018:ffffb2878f2cfc38 EFLAGS: 00010246
[Tue Mar 19 14:53:44 2024] RAX: 0000000000000000 RBX: ffff88d5171067b8 
RCX: 0000000000000000
[Tue Mar 19 14:53:44 2024] RDX: ffff88d517106880 RSI: ffff88bdceec8600 
RDI: 0000000000002000
[Tue Mar 19 14:53:44 2024] RBP: ffff88d68a38a284 R08: ffffb2878f2cfc00 
R09: 0000000000000000
[Tue Mar 19 14:53:44 2024] R10: ffff88bf57dd7878 R11: 0000000000000000 
R12: ffff88d5b79c4798
[Tue Mar 19 14:53:44 2024] R13: ffff88d68a38a270 R14: ffff88cab06ad0c8 
R15: ffff88d5b79c4798
[Tue Mar 19 14:53:44 2024] FS:  0000000000000000(0000) 
GS:ffff88d4a1180000(0000) knlGS:0000000000000000
[Tue Mar 19 14:53:44 2024] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[Tue Mar 19 14:53:44 2024] CR2: 00007fe46ef90000 CR3: 000000019d010004 
CR4: 00000000007706e0
[Tue Mar 19 14:53:44 2024] DR0: 0000000000000000 DR1: 0000000000000000 
DR2: 0000000000000000
[Tue Mar 19 14:53:44 2024] DR3: 0000000000000000 DR6: 00000000fffe0ff0 
DR7: 0000000000000400
[Tue Mar 19 14:53:44 2024] PKRU: 55555554
[Tue Mar 19 14:53:44 2024] Call Trace:
[Tue Mar 19 14:53:44 2024]  <TASK>
[Tue Mar 19 14:53:44 2024]  ? show_trace_log_lvl+0x1c4/0x2df
[Tue Mar 19 14:53:44 2024]  ? show_trace_log_lvl+0x1c4/0x2df
[Tue Mar 19 14:53:44 2024]  ? __break_lease+0x16f/0x5f0
[Tue Mar 19 14:53:44 2024]  ? nfsd_break_deleg_cb+0x170/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024]  ? __warn+0x81/0x110
[Tue Mar 19 14:53:44 2024]  ? nfsd_break_deleg_cb+0x170/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024]  ? report_bug+0x10a/0x140
[Tue Mar 19 14:53:44 2024]  ? handle_bug+0x3c/0x70
[Tue Mar 19 14:53:44 2024]  ? exc_invalid_op+0x14/0x70
[Tue Mar 19 14:53:44 2024]  ? asm_exc_invalid_op+0x16/0x20
[Tue Mar 19 14:53:44 2024]  ? nfsd_break_deleg_cb+0x170/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024]  ? nfsd_break_deleg_cb+0x96/0x190 [nfsd]
[Tue Mar 19 14:53:44 2024]  __break_lease+0x16f/0x5f0
[Tue Mar 19 14:53:44 2024]  nfs4_get_vfs_file+0x164/0x3a0 [nfsd]
[Tue Mar 19 14:53:44 2024]  nfsd4_process_open2+0x430/0xa30 [nfsd]
[Tue Mar 19 14:53:44 2024]  ? fh_verify+0x297/0x2f0 [nfsd]
[Tue Mar 19 14:53:44 2024]  nfsd4_open+0x3ce/0x4b0 [nfsd]
[Tue Mar 19 14:53:44 2024]  nfsd4_proc_compound+0x44b/0x700 [nfsd]
[Tue Mar 19 14:53:44 2024]  nfsd_dispatch+0x94/0x1c0 [nfsd]
[Tue Mar 19 14:53:44 2024]  svc_process_common+0x2ec/0x660 [sunrpc]
[Tue Mar 19 14:53:44 2024]  ? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
[Tue Mar 19 14:53:44 2024]  ? __pfx_nfsd+0x10/0x10 [nfsd]
[Tue Mar 19 14:53:44 2024]  svc_process+0x12d/0x170 [sunrpc]
[Tue Mar 19 14:53:44 2024]  nfsd+0x84/0xb0 [nfsd]
[Tue Mar 19 14:53:44 2024]  kthread+0xdd/0x100
[Tue Mar 19 14:53:44 2024]  ? __pfx_kthread+0x10/0x10
[Tue Mar 19 14:53:44 2024]  ret_from_fork+0x29/0x50
[Tue Mar 19 14:53:44 2024]  </TASK>
[Tue Mar 19 14:53:44 2024] ---[ end trace ed0b2b3f135c637d ]---

It again seems to have been triggered in nfsd_break_deleg_cb?

I also had the following perf command running a tmux on the server:

perf trace -e nfsd:nfsd_cb_recall_any

This has spewed a lot of messages. I'm including a short list here:

...

33464866.721 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688785, bmval0: 1, addr: 0x7f331bb116c8)
33464866.724 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688827, bmval0: 1, addr: 0x7f331bb11738)
33464866.729 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688767, bmval0: 1, addr: 0x7f331bb117a8)
33464866.732 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210718132, bmval0: 1, addr: 0x7f331bb11818)
33464866.737 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688952, bmval0: 1, addr: 0x7f331bb11888)
33464866.741 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210702355, bmval0: 1, addr: 0x7f331bb118f8)
33868414.001 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688751, bmval0: 1, addr: 0x7f331be68620)
33868414.014 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210718536, bmval0: 1, addr: 0x7f331be68690)
33868414.018 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210719074, bmval0: 1, addr: 0x7f331be68700)
33868414.022 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688916, bmval0: 1, addr: 0x7f331be68770)
33868414.026 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688941, bmval0: 1, addr: 0x7f331be687e0)
...

33868414.924 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688744, bmval0: 1, addr: 0x7f331be6d7f0)
33868414.929 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210717223, bmval0: 1, addr: 0x7f331be6d860)
33868414.934 kthreadd/1597068 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210716137, bmval0: 1, addr: 0x7f331be6d8d0)
34021240.903 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688941, bmval0: 1, addr: 0x7f331c207de8)
34021240.917 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210718750, bmval0: 1, addr: 0x7f331c207e58)
34021240.922 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688955, bmval0: 1, addr: 0x7f331c207ec8)
34021240.925 kworker/u98:5/1591466 nfsd:nfsd_cb_recall_any(cl_boot: 
1710533037, cl_id: 210688975, bmval0: 1, addr: 0x7f331c207f38)
...

I assume the cl_id is the client id? How can I map this to a client from 
/proc/fs/nfsd/clients?

If I understand it correctly, the recall_any should be called when 
either the system starts to experience memory pressure, or it reaches 
the delegation limits? I doubt the system is actually running out of 
memory here as there are no other indications. Shouldn't I get those 
"page allocation failure" messages if it does? How can I check the 
number of delegations/leases currently issued, what the current maximum 
is and how to increase it?

Regarding the recall any call: from what I've read on kernelnewbies, 
this feature was introduced in the 6.2 kernel? When I look at the tree 
for 6.1.x, it was backported in 6.1.81? Is there a way to disable this 
support somehow?

Regards,

Rik


>
> -Dai
>
>>>
>>>
>>>> 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?
>>>
>>> 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.
>>>
>>> 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.
>>
>> Regards,
>>
>> Rik
>>
>>>
>>> https://urldefense.com/v3/__https://wiki.centos.org/ReportBugs.html__;!!ACWV5N9M2RV99hQ!LV3yWeoSOhNAkRHkxFCH2tlm0iNFVD78mxnSLyP6lrX7yBVeA2TOJ4nv6oZsqLwP4kW56CMpDWhkjjwSkWIqsboq$ 
>>>
>>>
>>>>> 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
----------------------------------------------------------------
<<Any errors in spelling, tact or fact are transmission errors>>