Panic while doing zfs rename

Hi list,

First, excuse me to post on -current_at_ while this problem happened with
-STABLE but RELENG_8 is still relatively close to HEAD and I have the
feeling that -stable_at_ is more concerned with configuration and maybe
userland problems.

I've done the following command sequence on a fresh RELENG_8 from around
3rd dec:
    zfs send -R data/repos | zfs receive -d data/crepos
    zfs destroy data/repos
    zfs rename data/crepos/repos data/repos

And this led to the following panic on rename:

% Fatal trap 12: page fault while in kernel mode
% cpuid = 0; apic id = 00
% fault virtual address   = 0x780fe2a0
% fault code              = supervisor read, page not present
% instruction pointer     = 0x20:0x806d1687
% stack pointer           = 0x28:0xcb41c750
% frame pointer           = 0x28:0xcb41c784
% code segment            = base 0x0, limit 0xfffff, type 0x1b
%                         = DPL 0, pres 1, def32 1, gran 1
% processor eflags        = resume, IOPL = 0
% current process         = 72605 (zfs)
% [thread pid 72605 tid 100435 ]
% Stopped at      _sx_xlock_hard+0x21e:   movl    0x1a0(%eax),%eax
% db> bt
% Tracing pid 72605 tid 100435 td 0x88b6c480
% _sx_xlock_hard(8f2460a0,88b6c480,0,85ce8fc8,a1,...) at _sx_xlock_hard+0x21e
% _sx_xlock(8f2460a0,0,85ce8fc8,a1,866b2a70,...) at _sx_xlock+0x48
% rrw_enter(8f2460a0,1,85cdf7b1,0,cb41c7e8,...) at rrw_enter+0x35
% zfs_statfs(866b2a10,866b2a70,1d8,cb41c844,865a3a10,...) at zfs_statfs+0x39
% __vfs_statfs(866b2a10,cb41c844,0,0,0,...) at __vfs_statfs+0x1f
% nullfs_statfs(865a3a10,865a3a70,806bd68b,865a3a70,865a3a10,...) at nullfs_statfs+0x46
% __vfs_statfs(865a3a10,865a3a70,1d8,a5889340,cb41cb78,...) at __vfs_statfs+0x1f
% kern_getfsstat(88b6c480,cb41ccf8,8df8,0,1,...) at kern_getfsstat+0x2d0
% getfsstat(88b6c480,cb41ccf8,c,cb41ccb0,8096d28a,...) at getfsstat+0x2e
% syscall(cb41cd38) at syscall+0x320
% Xint0x80_syscall() at Xint0x80_syscall+0x20
% --- syscall (395, FreeBSD ELF32, getfsstat), eip = 0x281742d7, esp = 0x7fbfc8dc, ebp = 0x7fbfc908 ---


FYI, after the crash, I could rename the filesystem without any problem.

Regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >