zfs lor, panic

[Axel Scheepers]

Hello current list,

I've just installed -current on my amd64(smp) workstation and tried zfs 
a bit. I've setup my ports and src dir as gzip compressed zfs mounts and 
used it without any problems. Then I moved my homedir to zfs, and all 
went fine for a while.. until.. I tried to use rtorrent on a zfs volume. 
Suddenly zfs would take all vm.kmem_size and eventually paniced as 
described on this list before. I've set it to 512MB in /boot/loader.conf 
and restricted the ARC to 64MB+1, this didn't panic but gave my a lock 
order reversal and a system which completely spents it's time in system 
time (according to top 100% with 640MB kmem) slowing it down to nearly a 
halt.

I've captured one;
Apr 25 16:38:00 ceridwen kernel: lock order reversal:
Apr 25 16:38:00 ceridwen kernel: 1st 0xffffff0024654d70 user map (user 
map) @ /u
sr/src/sys/vm/vm_map.c:2172
Apr 25 16:38:00 ceridwen kernel: 2nd 0xffffff0027704dd8 zfs:&zp->z_lock 
(zfs:&zp
->z_lock) @ 
/usr/src/sys/modules/zfs/../../contrib/opensolaris/uts/common/fs/zfs
/zfs_znode.c:751
Apr 25 16:38:00 ceridwen kernel: KDB: stack backtrace:
Apr 25 16:38:00 ceridwen kernel: db_trace_self_wrapper() at 
db_trace_self_wrappe
r+0x3a
Apr 25 16:38:00 ceridwen kernel: witness_checkorder() at 
witness_checkorder+0x4f
9
Apr 25 16:38:00 ceridwen kernel: _sx_xlock() at _sx_xlock+0x3a
Apr 25 16:38:00 ceridwen kernel: zfs_time_stamper() at zfs_time_stamper+0x3c
Apr 25 16:38:00 ceridwen kernel: zfs_freebsd_write() at 
zfs_freebsd_write+0x780
Apr 25 16:38:00 ceridwen kernel: VOP_WRITE_APV() at VOP_WRITE_APV+0xa4
Apr 25 16:38:00 ceridwen kernel: vnode_pager_generic_putpages() at 
vnode_pager_g
eneric_putpages+0x218
Apr 25 16:38:00 ceridwen kernel: VOP_PUTPAGES_APV() at VOP_PUTPAGES_APV+0x77
Apr 25 16:38:00 ceridwen kernel: vnode_pager_putpages() at 
vnode_pager_putpages+
0x97
Apr 25 16:38:00 ceridwen kernel: vm_pageout_flush() at 
vm_pageout_flush+0x136
Apr 25 16:38:00 ceridwen kernel: vm_object_page_collect_flush() at 
vm_object_pag
e_collect_flush+0x2d1
Apr 25 16:38:00 ceridwen kernel: vm_object_page_clean() at 
vm_object_page_clean+
0x18e
Apr 25 16:38:00 ceridwen kernel: vm_object_sync() at vm_object_sync+0x239
Apr 25 16:38:00 ceridwen kernel: vm_map_sync() at vm_map_sync+0x107
Apr 25 16:38:00 ceridwen kernel: msync() at msync+0x66
Apr 25 16:38:00 ceridwen kernel: syscall() at syscall+0x1f0
Apr 25 16:38:00 ceridwen kernel: Xfast_syscall() at Xfast_syscall+0xab
Apr 25 16:38:00 ceridwen kernel: --- syscall (65, FreeBSD ELF64, msync), 
rip = 0
x8015a474c, rsp = 0x7fffffffe508, rbp = 0x801afd740 ---
Apr 25 16:43:35 ceridwen su: axel to root on /dev/ttyp0


I'm very pleased with zfs coming to freebsd; I've been using it on 
solaris for a while now with excellent results so far. I think this is 
described as not being dangerous but the side effects might cause severe 
effects/panics as far as I've noticed.


Kind regards,

Axel Scheepers