Kernel Panic of 10.2-RELEASE

[Stéphane Dupille]

Hello,

My server is running 10.2-RELEASE (yes, I need to upgrade it, but it works like a charm). Today, I launched this command, as root :
# zfs destroy -r zroot at attic
and the machine crashed :

Jul 18 18:09:40 penitencier syslogd: kernel boot file is /boot/kernel/kernel
Jul 18 18:09:40 penitencier kernel: vputx: negative ref count
Jul 18 18:09:40 penitencier kernel: 0xfffff8023037f000: tag zfs, type VDIR
Jul 18 18:09:40 penitencier kernel: usecount 0, writecount 0, refcount 0 mountedhere 0
Jul 18 18:09:40 penitencier kernel: flags (VI_FREE)
Jul 18 18:09:40 penitencier kernel: VI_LOCKed    lock type zfs: EXCL by thread 0xfffff8014f242940 (pid 60698, zfs, tid 100747)
Jul 18 18:09:40 penitencier kernel: panic: vputx: negative ref cnt
Jul 18 18:09:40 penitencier kernel: cpuid = 1
Jul 18 18:09:40 penitencier kernel: KDB: stack backtrace:
Jul 18 18:09:40 penitencier kernel: #0 0xffffffff80984ef0 at kdb_backtrace+0x60
Jul 18 18:09:40 penitencier kernel: #1 0xffffffff80948aa6 at vpanic+0x126
Jul 18 18:09:40 penitencier kernel: #2 0xffffffff80948973 at panic+0x43
Jul 18 18:09:40 penitencier kernel: #3 0xffffffff809eb7d5 at vputx+0x2d5
Jul 18 18:09:40 penitencier kernel: #4 0xffffffff809e4f59 at dounmount+0x689
Jul 18 18:09:40 penitencier kernel: #5 0xffffffff81a5fdd4 at zfs_unmount_snap+0x114
Jul 18 18:09:40 penitencier kernel: #6 0xffffffff81a62fc1 at zfs_ioc_destroy_snaps+0xc1
Jul 18 18:09:40 penitencier kernel: #7 0xffffffff81a61ae0 at zfsdev_ioctl+0x5f0
Jul 18 18:09:40 penitencier kernel: #8 0xffffffff80830019 at devfs_ioctl_f+0x139
Jul 18 18:09:40 penitencier kernel: #9 0xffffffff8099cde5 at kern_ioctl+0x255
Jul 18 18:09:40 penitencier kernel: #10 0xffffffff8099cae0 at sys_ioctl+0x140
Jul 18 18:09:40 penitencier kernel: #11 0xffffffff80d4b3e7 at amd64_syscall+0x357
Jul 18 18:09:40 penitencier kernel: #12 0xffffffff80d30acb at Xfast_syscall+0xfb
Jul 18 18:09:40 penitencier kernel: Uptime: 5d6h0m11s

This is all I found in logs. I have only a remote access to this machine so I have no clue of what was printed on console.

I use zfs on top of geom_eli.

Here is a uname -v :
FreeBSD penitencier.dalton-brothers.org 10.2-RELEASE-p9 FreeBSD 10.2-RELEASE-p9 #0: Thu Jan 14 01:32:46 UTC 2016     root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

After rebooting, the machine works well, as far as I can see :
root at penitencier:/var/log # zpool status
  pool: zboot
 state: ONLINE
  scan: scrub repaired 0 in 0h0m with 0 errors on Wed Nov 12 11:20:33 2014
config:

	NAME           STATE     READ WRITE CKSUM
	zboot          ONLINE       0     0     0
	  mirror-0     ONLINE       0     0     0
	    gpt/boot0  ONLINE       0     0     0
	    gpt/boot1  ONLINE       0     0     0

errors: No known data errors

  pool: zroot
 state: ONLINE
  scan: resilvered 6,56M in 0h0m with 0 errors on Tue Jul 18 18:13:23 2017
config:

	NAME           STATE     READ WRITE CKSUM
	zroot          ONLINE       0     0     0
	  mirror-0     ONLINE       0     0     0
	    da0p4.eli  ONLINE       0     0     0
	    da1p4.eli  ONLINE       0     0     0

errors: No known data errors


(the pool has been resilvered because I boot once, but put a wrong passphrase in geli for one of the two drives, so it booted with only one disk)

What should I do now ? launch a zfs scrub ? I’m a bit afraid of making it panic again. Should I consider that I got unlucky once ?
(please don’t tell me to upgrade it : I’m currently trying to install a new server, and I will migrate to it very soon).

Thanks.