Hi Jeff, On Sat, Jan 25, 2025 at 05:55:50PM -0500, Jeff Layton wrote: > On Sat, 2025-01-25 at 21:44 +0100, Salvatore Bonaccorso wrote: > > Hi Chuck, Jeff, NFSD maintainers, > > > > In Debian we got a report from a user which triggered an issue during > > package updates hwere nfs-kernel-server restart was involved, then > > hanging and included a kernel trace of a NULL pointer dereference. > > > > The full report is at: > > https://bugs.debian.org/1093734 > > > > While I was not able to trigger the issue, the provided log is as > > follows: > > > > 2025-01-21T12:07:01.516291+01:00 $HOST kernel: device-mapper: core: CONFIG_IMA_DISABLE_HTABLE is disabled. Duplicate IMA measurements will not be recorded in the IMA log. > > 2025-01-21T12:07:01.516310+01:00 $HOST kernel: device-mapper: uevent: version 1.0.3 > > 2025-01-21T12:07:01.516312+01:00 $HOST kernel: device-mapper: ioctl: 4.48.0-ioctl (2023-03-01) initialised: dm-devel@xxxxxxxxxxxxxxx > > 2025-01-21T12:07:13.528044+01:00 $HOST kernel: NFSD: Using nfsdcld client tracking operations. > > 2025-01-21T12:07:13.528061+01:00 $HOST kernel: NFSD: no clients to reclaim, skipping NFSv4 grace period (net f0000000) > > 2025-01-21T12:07:17.558915+01:00 $HOST blkmapd[1148]: exit on signal(15) > > 2025-01-21T12:07:17.574410+01:00 $HOST blkmapd[239859]: open pipe file /run/rpc_pipefs/nfs/blocklayout failed: No such file or directory > > 2025-01-21T12:07:18.015541+01:00 $HOST kernel: BUG: kernel NULL pointer dereference, address: 0000000000000090 > > Thanks for the bug report. It's getting late here, so I can only take a > quick look. svc_wake_up is pretty small: > > void svc_wake_up(struct svc_serv *serv) > { > struct svc_pool *pool = &serv->sv_pools[0]; > > set_bit(SP_TASK_PENDING, &pool->sp_flags); > svc_pool_wake_idle_thread(pool); > } > > pahole on my machine says that struct svc_serv has this at offset 0x90: > > struct svc_pool * sv_pools; /* 0x90 0x8 */ > > So it looks like the nn->nfsd_serv was a NULL pointer. That only > happens when we shut down the server, so this looks like a race between > filecache garbage collection with shutdown. > > The filecache gets shut down in nfsd_shutdown_net, which gets called > _after_ setting the nn->nfsd_serv pointer to NULL. We'll have to look > at whether we can reorder the NULL pointer setting to later, or work > around this some other way. > > Could I trouble you to open a bug for this at bugzilla.kernel.org? Thanks a lot for your quick response on it and the analysis. Sure I can fill a bug in bugzilla.kernel.org, I see you submitted a patch already, do you still want me to do it? If so I try to reference as well all followups so that the information is not spread around threads. Thanks a lot for your work! Regards, Salvatore
