Hi, On Fri, Jan 10, 2025 at 11:07 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > > On 1/10/25 3:51 PM, Rik Theys wrote: > > Hi, > > > > Thanks for your prompt reply. > > > > On Fri, Jan 10, 2025 at 9:30 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > >> > >> On 1/10/25 2:49 PM, Rik Theys wrote: > >>> Hi, > >>> > >>> Our Rocky 9 NFS server running the upstream 6.11.11 kernel is starting > >>> to log the following hung task messages: > >>> > >>> INFO: task kworker/u194:11:1677933 blocked for more than 215285 seconds. > >>> Tainted: G W E 6.11.11-1.el9.esat.x86_64 #1 > >>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > >>> task:kworker/u194:11 state:D stack:0 pid:1677933 tgid:1677933 > >>> ppid:2 flags:0x00004000 > >>> Workqueue: nfsd4 laundromat_main [nfsd] > >>> Call Trace: > >>> <TASK> > >>> __schedule+0x21c/0x5d0 > >>> ? preempt_count_add+0x47/0xa0 > >>> schedule+0x26/0xa0 > >>> nfsd4_shutdown_callback+0xea/0x120 [nfsd] > >>> ? __pfx_var_wake_function+0x10/0x10 > >>> __destroy_client+0x1f0/0x290 [nfsd] > >>> nfs4_process_client_reaplist+0xa1/0x110 [nfsd] > >>> nfs4_laundromat+0x126/0x7a0 [nfsd] > >>> ? _raw_spin_unlock_irqrestore+0x23/0x40 > >>> laundromat_main+0x16/0x40 [nfsd] > >>> process_one_work+0x179/0x390 > >>> worker_thread+0x239/0x340 > >>> ? __pfx_worker_thread+0x10/0x10 > >>> kthread+0xdb/0x110 > >>> ? __pfx_kthread+0x10/0x10 > >>> ret_from_fork+0x2d/0x50 > >>> ? __pfx_kthread+0x10/0x10 > >>> ret_from_fork_asm+0x1a/0x30 > >>> </TASK> > >>> > >>> If I read this correctly, it seems to be blocked on a callback > >>> operation during shutdown of a client connection? > >>> > >>> Is this a known issue that may be fixed in the 6.12.x kernel? Could > >>> the following commit be relevant? > >> > >> It is a known issue that we're just beginning to work. It's not > >> addressed in any kernel at the moment. > >> > >> > >>> 8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a nfsd: fix race between > >>> laundromat and free_stateid > >>> > >>> If I increase the hung_task_warnings sysctl and wait a few minutes, > >>> the hung task message appears again, so the issue is still present on > >>> the system. How can I debug which client is causing this issue? > >>> > >>> Is there any other information I can provide? > >> > >> Yes. We badly need a simple reproducer for this issue so that we > >> can test and confirm that it is fixed before requesting that any > >> fix is merged. > > > > Unfortunately, we've been unable to reliably reproduce the issue on > > our test systems. Sometimes the server works fine for weeks, and > > sometimes these (or other) issues pop up within hours. Similar to the > > users from the mentioned thread, we let a few hundred engineers and > > students loose. Our clients are both EL8/9 based, and also Fedora 41, > > and they (auto)mount home directories from the NFS server. So clients > > frequently mount and unmount file systems, students uncleanly shut > > down systems,... > > > > We switched to the mainline kernel in the hope this would include a > > fix for the issue. > > > > Are there any debugging commands we can run once the issue happens > > that can help to determine the cause of this issue? > > Once the issue happens, the precipitating bug has already done its > damage, so at that point it is too late. > > If you can start a trace command on the server before clients mount > it, try this: > > # trace-cmd record -e nfsd:nfsd_cb_\* > > After the issue has occurred, wait a few minutes then ^C this command > and send me the trace.dat. > I can create a systemd unit to start this command when the system boots and stop it when the issue happens. What is the expected performance impact of keeping this tracing running? Is there an easy way to rotate the trace.dat file as I assume it will grow quite large? > The current theory is that deleg_reaper() is running concurrently with > the client's DESTROY_SESSION request, and that leaves callback RPCs > outstanding when the callback RPC client is destroyed. Session shutdown > then hangs waiting for a completion that will never fire. Would it be possible to capture this using a bpftrace script? If so, which events would be interesting to capture to confirm this theory? Is there an easy way to forcefully trigger the deleg_reaper to run so we can try running it in a loop and then reboot/unmount the client in an attempt to trigger the issue? > > If your server runs chronically short on physical memory, that might > be a trigger. Before the server was upgraded to EL9, it ran CentOS 7 for 5 years without any issue and we never experienced any physical memory shortage. Why does the system think it's running low on memory and needs to send the RECALL_ANY callbacks? It never did in the past and the system seemed to do fine. Is there a way to turn off the RECALL_ANY callbacks (at runtime)? > > > >> An environment where we can test patches against the upstream > >> kernel would also be welcome. Our current plan is to run the 6.12 kernel as this is an LTS kernel. If there are patches for this kernel version we can try, we may be able to apply them. But we can't reboot the system every few days as hundreds of people depend on it. It can also take quite some time to actually trigger it (or assume it was fixed by a patch). Regards, Rik > >> > >> > >>> Could this be related to the following thread: > >>> https://lore.kernel.org/linux-nfs/Z2vNQ6HXfG_LqBQc@xxxxxxxxxxx/T/#u ? > >> > >> Yes. > >> > >> > >>> I don't know if this is relevant but I've noticed that some clients > >>> have multiple entries in the /proc/fs/nfsd/clients directory, so I > >>> assume these clients are not cleaned up correctly? > > > > You don't think this is relevant for this issue? Is this normal? > > It might be a bug, but I can't say whether it's related. > > > >>> For example: > >>> > >>> clientid: 0x6d077c99675df2b3 > >>> address: "10.87.29.32:864" > >>> status: confirmed > >>> seconds from last renew: 0 > >>> name: "Linux NFSv4.2 betelgeuse.esat.kuleuven.be" > >>> minor version: 2 > >>> Implementation domain: "kernel.org" > >>> Implementation name: "Linux 4.18.0-553.32.1.el8_10.x86_64 #1 SMP Wed > >>> Dec 11 16:33:48 UTC 2024 x86_64" > >>> Implementation time: [0, 0] > >>> callback state: UP > >>> callback address: 10.87.29.32:0 > >>> admin-revoked states: 0 > >>> *** > >>> clientid: 0x6d0596d0675df2b3 > >>> address: "10.87.29.32:864" > >>> status: courtesy > >>> seconds from last renew: 2288446 > >>> name: "Linux NFSv4.2 betelgeuse.esat.kuleuven.be" > >>> minor version: 2 > >>> Implementation domain: "kernel.org" > >>> Implementation name: "Linux 4.18.0-553.32.1.el8_10.x86_64 #1 SMP Wed > >>> Dec 11 16:33:48 UTC 2024 x86_64" > >>> Implementation time: [0, 0] > >>> callback state: UP > >>> callback address: 10.87.29.32:0 > >>> admin-revoked states: 0 > >>> > >>> The first one has status confirmed and the second one "courtesy" with > >>> a high "seconds from last renew". The address and port matches for > >>> both client entries and the callback state is both UP. > >>> > >>> For another client, there's a different output: > >>> > >>> clientid: 0x6d078a79675df2b3 > >>> address: "10.33.130.34:864" > >>> status: unconfirmed > >>> seconds from last renew: 158910 > >>> name: "Linux NFSv4.2 bujarski.esat.kuleuven.be" > >>> minor version: 2 > >>> Implementation domain: "kernel.org" > >>> Implementation name: "Linux 5.14.0-503.19.1.el9_5.x86_64 #1 SMP > >>> PREEMPT_DYNAMIC Thu Dec 19 12:55:03 UTC 2024 x86_64" > >>> Implementation time: [0, 0] > >>> callback state: UNKNOWN > >>> callback address: (einval) > >>> admin-revoked states: 0 > >>> *** > >>> clientid: 0x6d078a7a675df2b3 > >>> address: "10.33.130.34:864" > >>> status: confirmed > >>> seconds from last renew: 2 > >>> name: "Linux NFSv4.2 bujarski.esat.kuleuven.be" > >>> minor version: 2 > >>> Implementation domain: "kernel.org" > >>> Implementation name: "Linux 5.14.0-503.19.1.el9_5.x86_64 #1 SMP > >>> PREEMPT_DYNAMIC Thu Dec 19 12:55:03 UTC 2024 x86_64" > >>> Implementation time: [0, 0] > >>> callback state: UP > >>> callback address: 10.33.130.34:0 > >>> admin-revoked states: 0 > >>> > >>> > >>> Here the first status is unconfirmed and the callback state is UNKNOWN. > >>> > >>> The clients are Rocky 8, Rocky 9 and Fedora 41 clients. > >>> > >>> Regards, > >>> > >>> Rik > >>> > >> > >> > >> -- > >> Chuck Lever > > > > > -- > Chuck Lever -- Rik
