zfs diff caused kernel panic

[Claudius Herder]

Hi all,

i received a kernel panic after running zfs diff on system/rootfs, other
filesystems work without problems.

Apr 15 21:11:17 server kernel: Fatal trap 9: general protection fault
while in kernel mode
Apr 15 21:11:17 server kernel: cpuid = 3; apic id = 03
Apr 15 21:11:17 server kernel: instruction pointer      =
0x20:0xffffffff80b0ff91
Apr 15 21:11:17 server kernel: stack pointer            =
0x28:0xffffff845fa1b430
Apr 15 21:11:17 server kernel: frame pointer            =
0x28:0xffffff845fa1b470
Apr 15 21:11:17 server kernel: code segment             = base 0x0,
limit 0xfffff, type 0x1b
Apr 15 21:11:17 server kernel: = DPL 0, pres 1, long 1, def32 0, gran 1
Apr 15 21:11:17 server kernel: processor eflags = interrupt enabled,
resume, IOPL = 0
Apr 15 21:11:17 server kernel: current process          = 1797 (zfs)
Apr 15 21:11:17 server kernel: trap number              = 9
Apr 15 21:11:17 server kernel: panic: general protection fault
Apr 15 21:11:17 server kernel: cpuid = 3
Apr 15 21:11:17 server kernel: KDB: stack backtrace:
Apr 15 21:11:17 server kernel: #0 0xffffffff803fcb5e at kdb_backtrace+0x5e
Apr 15 21:11:17 server kernel: #1 0xffffffff803c9ce3 at panic+0x183
Apr 15 21:11:17 server kernel: #2 0xffffffff805c49a0 at trap_fatal+0x290
Apr 15 21:11:17 server kernel: #3 0xffffffff805c4eda at trap+0x10a
Apr 15 21:11:17 server kernel: #4 0xffffffff805af7ef at calltrap+0x8
Apr 15 21:11:17 server kernel: #5 0xffffffff80b0f0e0 at
fzap_cursor_retrieve+0x110
Apr 15 21:11:17 server kernel: #6 0xffffffff80b13bc5 at
zap_cursor_retrieve+0x155
Apr 15 21:11:17 server kernel: #7 0xffffffff80b0e12f at
zap_value_search+0x7f
Apr 15 21:11:17 server kernel: #8 0xffffffff80b18912 at
zfs_obj_to_path_impl+0x292
Apr 15 21:11:17 server kernel: #9 0xffffffff80b18b45 at
zfs_obj_to_stats+0x175
Apr 15 21:11:17 server kernel: #10 0xffffffff80b3075e at
zfs_ioc_obj_to_stats+0x7e
Apr 15 21:11:17 server kernel: #11 0xffffffff80b33a46 at zfsdev_ioctl+0xe6
Apr 15 21:11:17 server kernel: #12 0xffffffff8034e4db at devfs_ioctl_f+0x7b
Apr 15 21:11:17 server kernel: #13 0xffffffff8040e185 at kern_ioctl+0x115
Apr 15 21:11:17 server kernel: #14 0xffffffff8040e3b0 at sys_ioctl+0xf0
Apr 15 21:11:17 server kernel: #15 0xffffffff805c4290 at amd64_syscall+0x450
Apr 15 21:11:17 server kernel: #16 0xffffffff805afad7 at Xfast_syscall+0xf7

I tried different snapshots on rootfs to narrow down then problem, but
after a few forced reboots and zpool scrub after each crash zfs diff
hangs only.

procstat -k -k 8428
 PID    TID COMM             TDNAME           KSTACK
 8428 100719 zfs              -                mi_switch+0x174
sleepq_catch_signals+0x2f4 sleepq_wait_sig+0xc _sleep+0x279
pipe_write+0x125e write_record+0x79 report_free_dnode_range+0x2c
diff_cb+0x1bf traverse_visitbp+0x21c traverse_visitbp+0x309
traverse_visitbp+0x309 traverse_visitbp+0x309 traverse_visitbp+0x309
traverse_visitbp+0x309 traverse_visitbp+0x309 traverse_dnode+0x7c
traverse_visitbp+0x47f traverse_impl+0x188
 8428 101237 zfs              -                mi_switch+0x174
sleepq_wait+0x42 _sx_slock_hard+0x1f2 _sx_slock+0x45
zap_get_leaf_byblk+0xbd zap_deref_leaf+0x68 fzap_cursor_retrieve+0xe7
zap_cursor_retrieve+0x155 zap_value_search+0x7f
zfs_obj_to_path_impl+0x292 zfs_obj_to_stats+0x175
zfs_ioc_obj_to_stats+0x7e zfsdev_ioctl+0xe6 devfs_ioctl_f+0x7b
kern_ioctl+0x115 sys_ioctl+0xf0 amd64_syscall+0x450 Xfast_syscall+0xf7

Any hints how to debug this further?

--
Regards and thanks in advance

Claudius

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