Panic using rsync to msdosfs filesystem

I have a western digital passport USB hard drive that I use for 
backups. It's always worked fine in FreeBSD and Windows doing straight 
copies. Today I tried to get fancy and use rsync and it blew up on me.

It is a large disk (160G) and I use the following options in fstab:
/dev/da0s1  /mnt/wd  msdosfs  rw,noauto,-olarge,-m775  0  0

Using the following command line for rsync I get a panic as soon as I 
hit return: rsync -vv --backup -u -rlt source/ destination/

I'm using -current as of r180191. Here is the stack trace:
Unread portion of the kernel message buffer:
panic: stack overflow detected; backtrace may be corrupted
cpuid = 1
Uptime: 1h52m1s
Physical memory: 2029 MB
Dumping 133 MB: 118 102 86 70 54 38 22 6

Reading symbols from /boot/modules/nvidia.ko...Reading symbols from 
/boot/modules/nvidia.ko.symbols...done.
done.
Loaded symbols for /boot/modules/nvidia.ko
Reading symbols from /boot/kernel/acpi.ko...Reading symbols from 
/boot/kernel/acpi.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/acpi.ko
Reading symbols from /boot/kernel/if_bge.ko...Reading symbols from 
/boot/kernel/if_bge.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/if_bge.ko
Reading symbols from /boot/kernel/linux.ko...Reading symbols from 
/boot/kernel/linux.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linux.ko
Reading symbols from /boot/kernel/msdosfs.ko...Reading symbols from 
/boot/kernel/msdosfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/msdosfs.ko
#0  doadump () at pcpu.h:196
196		__asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) where
#0  doadump () at pcpu.h:196
#1  0xc057a9ce in boot (howto=260)
     at /usr/local/src/sys/kern/kern_shutdown.c:418
#2  0xc057ac93 in panic (fmt=Variable "fmt" is not available.
) at /usr/local/src/sys/kern/kern_shutdown.c:572
#3  0xc059c5b2 in __stack_chk_fail ()
     at /usr/local/src/sys/kern/stack_protector.c:17
#4  0xc652384a in msdosfs_rename (ap=0xc644aca4)
     at 
/usr/local/src/sys/modules/msdosfs/../../fs/msdosfs/msdosfs_vnops.c:1286
#5  0xc07b4df5 in VOP_RENAME_APV (vop=0xc6525cc0, a=0xe9e59c1c)
     at vnode_if.c:1184
#6  0xc0605619 in kern_renameat (td=0xc58f1d20, oldfd=-100,
     old=0xbfbfc4a0 <Address 0xbfbfc4a0 out of bounds>, newfd=-100,
     new=0xbfbfcca0 <Address 0xbfbfcca0 out of bounds>, 
pathseg=UIO_USERSPACE)
     at vnode_if.h:622
#7  0xc06057a6 in kern_rename (td=0xc58f1d20,
     from=0xbfbfc4a0 <Address 0xbfbfc4a0 out of bounds>,
     to=0xbfbfcca0 <Address 0xbfbfcca0 out of bounds>, 
pathseg=UIO_USERSPACE)
     at /usr/local/src/sys/kern/vfs_syscalls.c:3526
#8  0xc06057d9 in rename (td=0xc58f1d20, uap=0xe9e59cf8)
     at /usr/local/src/sys/kern/vfs_syscalls.c:3503
#9  0xc07a6283 in syscall (frame=0xe9e59d38)
     at /usr/local/src/sys/i386/i386/trap.c:1081
#10 0xc078bb80 in Xint0x80_syscall ()
     at /usr/local/src/sys/i386/i386/exception.s:261
#11 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)


Let me know what I can do to help.

Doug

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