question on extended attributes

[Daniel Mayfield]

>>>> rsync: rsync_xal_set: lsetxattr("Documents/<foo>","com.apple.ResourceFork") failed: No space left on device (28)
>>> 
>>> Sorry if this sounds harsh or rude, but can I ask you what exactly
>>> extended filesystem attributes (usually ACLs) have to do with file
>>> resource forks on OS X?  AFAIK they have nothing to do with one another.
>> 
>> OS X stores resource forks (and a few other things) as extended attributes on HFS+ filesystems these days.  Or at least that's how it presents the HFS+ concept of a resource fork to unix programs like rsync that understand extended attributes.
> 
> I'll assume you're right.  With that assumption in place: OS X rsync
> supports extended attributes, which when used (on an OS X client) reads
> data from HFS+ extattr.
> 
> How exactly do you expect this data to be saved on a non-HFS+
> filesystem, such as BSD FFS/UFS, or Linux ext2fs, or Solaris UFS?  How
> will rsync (on the server side, meaning the process that's actually
> writing the data to a file on the filesystem) know what to do with this
> data?
> 
> The only way this would be possible is if rsync had its own custom way
> of saving resource forks on a remote system (they would have to be
> separate files).  Restoration would require that rsync know what to do
> with some "specially-named files" to represent the resource fork
> portion.  Keep reading for an example.

Rsync sees it as an extended attribute, a black box as it were, and simply copies it byte for byte to the remote side which then attempts to store the (very large) extended attribute.  That's where the above message comes from (rsync <remote>: "." .  on the freebsd box is what is emitting the no space left message).

I fully admit that its a bit of a hack, but I'm just looking for a place to start within the code so I can try to allow for arbitrarily sized extended attributes (or at least allocate an inode for large extattrs).  Google gives me this: http://lists.samba.org/archive/rsync/2009-October/024124.html which confirms that the size limit of the extattr is to blame.  The poster there had a similar idea to what you described, but I'm not satisfied with that.

daniel