This may be a linux issue. Found the error, happening daily around mid night - is this a schedule journal rotation causing a problem? Also not sure if the NFS is the cause or the victim.
2021-05-29T00:00:02,213050-07:00 kauditd_printk_skb: 23 callbacks suppressed
2021-05-29T00:00:02,213054-07:00 audit: type=1400 audit(1622271603.118:35): apparmor="DENIED" operation="capable" profile="/usr/sbin/cups-browsed" pid=3630 comm="cups-browsed" capability=23 capname="sys_nice"
2021-05-29T00:12:02,777335-07:00 INFO: task jbd2/sdb-8:2016 blocked for more than 120 seconds.
2021-05-29T00:12:02,777345-07:00 Not tainted 5.8.0-53-generic #60~20.04.1-Ubuntu
2021-05-29T00:12:02,777348-07:00 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2021-05-29T00:12:02,777352-07:00 jbd2/sdb-8 D 0 2016 2 0x00004000
2021-05-29T00:12:02,777358-07:00 Call Trace:
2021-05-29T00:12:02,777378-07:00 __schedule+0x394/0xa60
2021-05-29T00:12:02,777387-07:00 ? sched_clock+0x9/0x10
2021-05-29T00:12:02,777391-07:00 schedule+0x55/0xc0
2021-05-29T00:12:02,777399-07:00 jbd2_journal_commit_transaction+0x258/0x17f0
2021-05-29T00:12:02,777403-07:00 ? sched_clock+0x9/0x10
2021-05-29T00:12:02,777410-07:00 ? sched_clock_cpu+0x11/0xb0
2021-05-29T00:12:02,777416-07:00 ? wait_woken+0x80/0x80
2021-05-29T00:12:02,777423-07:00 ? try_to_del_timer_sync+0x54/0x80
2021-05-29T00:12:02,777427-07:00 kjournald2+0xb6/0x280
2021-05-29T00:12:02,777430-07:00 ? wait_woken+0x80/0x80
2021-05-29T00:12:02,777435-07:00 kthread+0x114/0x150
2021-05-29T00:12:02,777438-07:00 ? commit_timeout+0x20/0x20
2021-05-29T00:12:02,777440-07:00 ? kthread_park+0x90/0x90
2021-05-29T00:12:02,777446-07:00 ret_from_fork+0x22/0x30
2021-05-29T00:12:02,777509-07:00 INFO: task nfsd:2419 blocked for more than 120 seconds.
2021-05-29T00:12:02,777512-07:00 Not tainted 5.8.0-53-generic #60~20.04.1-Ubuntu
2021-05-29T00:12:02,777514-07:00 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2021-05-29T00:12:02,777517-07:00 nfsd D 0 2419 2 0x00004000
2021-05-29T00:12:02,777520-07:00 Call Trace:
2021-05-29T00:12:02,777525-07:00 __schedule+0x394/0xa60
2021-05-29T00:12:02,777529-07:00 schedule+0x55/0xc0
2021-05-29T00:12:02,777535-07:00 rwsem_down_write_slowpath+0x239/0x4b0
2021-05-29T00:12:02,777542-07:00 down_write+0x41/0x50
2021-05-29T00:12:02,777549-07:00 ext4_buffered_write_iter+0x38/0x140
2021-05-29T00:12:02,777552-07:00 ext4_file_write_iter+0x50/0x220
2021-05-29T00:12:02,777561-07:00 do_iter_readv_writev+0x13f/0x1b0
2021-05-29T00:12:02,777566-07:00 do_iter_write+0x88/0x1b0
2021-05-29T00:12:02,777568-07:00 vfs_iter_write+0x19/0x30
2021-05-29T00:12:02,777598-07:00 nfsd_vfs_write+0x25d/0x560 [nfsd]
2021-05-29T00:12:02,777621-07:00 nfsd4_write+0x150/0x1e0 [nfsd]
2021-05-29T00:12:02,777642-07:00 nfsd4_proc_compound+0x3c2/0x760 [nfsd]
2021-05-29T00:12:02,777664-07:00 ? nfsd4_decode_compound.constprop.0+0x3a9/0x450 [nfsd]
2021-05-29T00:12:02,777682-07:00 nfsd_dispatch+0xe2/0x220 [nfsd]
2021-05-29T00:12:02,777719-07:00 svc_process_common+0x47b/0x6f0 [sunrpc]
2021-05-29T00:12:02,777749-07:00 ? svc_sock_secure_port+0x16/0x30 [sunrpc]
2021-05-29T00:12:02,777766-07:00 ? nfsd_svc+0x330/0x330 [nfsd]
2021-05-29T00:12:02,777796-07:00 svc_process+0xbc/0xf0 [sunrpc]
2021-05-29T00:12:02,777813-07:00 nfsd+0xe8/0x150 [nfsd]
2021-05-29T00:12:02,777816-07:00 kthread+0x114/0x150
2021-05-29T00:12:02,777832-07:00 ? nfsd_destroy+0x60/0x60 [nfsd]
2021-05-29T00:12:02,777834-07:00 ? kthread_park+0x90/0x90
2021-05-29T00:12:02,777838-07:00 ret_from_fork+0x22/0x30
