[OpenAFS-devel] AFS vs UNICODE

[Erik Dalén]

On Tue, May 6, 2008 at 4:57 PM, Jeffrey Altman
<jaltman@secure-endpoints.com> wrote:
> Derrick Brashear wrote:
>>>
>>>  Note that the problem is worse than might be inferred from your
>>>  description.  If a fileserver is installed which behaves as you sugges=
t,
>>>  then when a MacOS X client creates a file with a name for which NFC an=
d
>>>  NFD produce different code sequences, the fileserver will normalize to
>>> NFC
>>>  before creating the directory entry, and MacOS will be unable to look =
up
>>>  the entry in the resulting directory.  It'll be subtle, too, because t=
he
>>>  MacOS client will update its local copy of the directory itself, with
>>> the
>>>  NFD filename, and won't notice the fileserver's change until either th=
at
>>>  directory is changed by some other client or the directory data is
>>> evicted
>>>  from the MacOS client's cache (note that callback expiration is _not_
>>>  sufficient here -- the client can use "old" data in its cache as long =
as
>>>  it does a new RXAFS_FetchStatus and notices the DV hasn't changed).
>>
>> I'm thinking there's a trick to be done with an "unexpected" DV change
>> such that LocalHero doesn't apply, avoiding this issue and forcing a
>> refetch.
>
> I still don't think that is going to do the right thing.
> That will permit the old MacoS X client to create the file.  It will
> read the directory with the new name in it.  And then be unable to open
> it because NFD != NFC and the hash table lookup will fail.
>
> I'm so sad.
>
>

The git list had a discussion about this same issue, and from their
testing is seems like most other file system drivers for Mac OS X
translate between UTF-8 NFD and NFC.

According to this post at least SMB, MSDOS, UDF, ISO 9660 (Joliet),
NTFS and ZFS file systems do this. HFS+ stores the files in NFD
natively.

http://kerneltrap.org/mailarchive/git/2008/1/23/593749

Another subtlety is that they use different types of NFD in Mac OS X
< 10.3.0 and >= 10.3.0.

Lots of fun in other words, but as most other file system drivers does
it it seems logical to do it in the AFS client for Mac as well.

-- 
Erik Dalén