ZFS panic in zone_dataset_visible

Hello,

I am running several servers using Pawel's July 27 ZFS patchset, applied 
against 8-current source from the same day.  I have seen a similar panic 
on two different servers:

Server #1:

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x570
fault code              = supervisor write data, page not present
instruction pointer     = 0x8:0xffffffff802d60a5
stack pointer           = 0x10:0xfffffffec89f3280
frame pointer           = 0x10:0xfffffffec89f3290
code segment            = base 0x0, limit 0xfffff, type 0x1b
                         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 95276 (ftpd)
[thread pid 95276 tid 100432 ]
Stopped at      _mtx_lock_flags+0x15:   lock cmpxchgq   %rsi,0x18(%rdi)
db> bt
Tracing pid 95276 tid 100432 td 0xffffff010b3cc000
_mtx_lock_flags() at _mtx_lock_flags+0x15
zone_dataset_visible() at zone_dataset_visible+0x94
zfs_mount() at zfs_mount+0x3e5
domount() at domount+0x216
zfsctl_snapdir_lookup() at zfsctl_snapdir_lookup+0x3ba
VOP_LOOKUP_APV() at VOP_LOOKUP_APV+0x40
lookup() at lookup+0x518
namei() at namei+0x515
kern_statat() at kern_statat+0x92
lstat() at lstat+0x2a
syscall() at syscall+0x264
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (190, FreeBSD ELF64, lstat), rip = 0x800d9153c, rsp = 
0x7fffffffa5c8, rbp = 0x6581d0 ---
db>

Server #1 (again):

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x570
fault code              = supervisor write data, page not present
instruction pointer     = 0x8:0xffffffff802d60a5
stack pointer           = 0x10:0xfffffffec8b3d280
frame pointer           = 0x10:0xfffffffec8b3d290
code segment            = base 0x0, limit 0xfffff, type 0x1b
                         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 87967 (sftp-server)
[thread pid 87967 tid 100498 ]
Stopped at      _mtx_lock_flags+0x15:   lock cmpxchgq   %rsi,0x18(%rdi)
db> bt
Tracing pid 87967 tid 100498 td 0xffffff00a4c81700
_mtx_lock_flags() at _mtx_lock_flags+0x15
zone_dataset_visible() at zone_dataset_visible+0x94
zfs_mount() at zfs_mount+0x3e5
domount() at domount+0x216
zfsctl_snapdir_lookup() at zfsctl_snapdir_lookup+0x3ba
VOP_LOOKUP_APV() at VOP_LOOKUP_APV+0x40
lookup() at lookup+0x518
namei() at namei+0x515
kern_statat() at kern_statat+0x92
lstat() at lstat+0x2a
syscall() at syscall+0x264
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (190, FreeBSD ELF64, lstat), rip = 0x800d1c53c, rsp = 
0x7ffffffea5b8, rbp = 0x630020 ---
db>

Server #2:

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x570
fault code              = supervisor write data, page not present
instruction pointer     = 0x8:0xffffffff802d60a5
stack pointer           = 0x10:0xfffffffec8813280
frame pointer           = 0x10:0xfffffffec8813290
code segment            = base 0x0, limit 0xfffff, type 0x1b
                         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 2851 (sh)
[thread pid 2851 tid 100336 ]
Stopped at      _mtx_lock_flags+0x15:   lock cmpxchgq   %rsi,0x18(%rdi)
db> bt
Tracing pid 2851 tid 100336 td 0xffffff004f0cf000
_mtx_lock_flags() at _mtx_lock_flags+0x15
zone_dataset_visible() at zone_dataset_visible+0x94
zfs_mount() at zfs_mount+0x3e5
domount() at domount+0x216
zfsctl_snapdir_lookup() at zfsctl_snapdir_lookup+0x3ba
VOP_LOOKUP_APV() at VOP_LOOKUP_APV+0x40
lookup() at lookup+0x518
namei() at namei+0x515
kern_statat() at kern_statat+0x92
stat() at stat+0x2a
syscall() at syscall+0x264
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (188, FreeBSD ELF64, stat), rip = 0x80099855c, rsp = 
0x7fffffffe868, rbp = 0x1 ---
db>

Has anyone else encountered this panic?

--
Scott Burns
System Administrator
BQ Internet Corporation