Write attempt to file in ZFS snapshot dir causes panic

[Carl Chave]

I'm new to FreeBSD.  Been experimenting with 8.0-RC1 and zfs in a VM.
Really haven't even installed it yet, just getting familiar with zfs
usage from the fixit environment.  I experienced some strange behavior
and was wondering if this would warrant a bug report:

1. load zfs from bootloader prompt and then boot.
2. enter fixit environment.
3. import zpool (in this case a 2 disk vmware mirror named sodpool)
4. cd to previously created snapshot at sodpool/test/myfs/.zfs/snapshot/one
5. attempting to create a new file here results in:

Fixit# echo hello > hello.txt
cannot create hello.txt: Read-only file system

6. That seems like the desired response.  Next, attempt to modify a
file that already exists in the snapshot:

Fixit# echo hello >> test.txt
panic: dirtying snapshot!

I know I'm not supposed to be modifying a snapshot file, but a panic
doesn't seem like the best response to this situation.

I'm using DVD iso named 8.0-RC1-amd64-dvd1.iso

This bug report has the same panic but the scenario is different:
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/138764

Is there someplace else I should check for existing issues?