>> No [copying files with metadata] can't [be done in userspace]. Example:
>>
>> /home/bob is a Windows share, mounted from an NT server.
>> Bob does "cp foo bar" to make a copy of his file.
>>
>> That file has:
>> * ACLs
>> * multiple forks
>> * extended attributes
>> * several gigabytes of data
>> * holes (compression)
>>
>> Now, you want to haul several gigabytes of data over 10baseT
>
> Bob obviously does. Or are you suggesting cp should know what kind of
> file system it's using, from what kind of clients, and use some kind of
> RPC call when possible?
The kernel is aware of the filesystem type, so the kernel can use
some kind of RPC call when possible. That is much cleaner than
a setuid /bin/cp that bypasses the kernel.
>> and lose all the information that Linux can't understand???
>
> It depends on how that information is presented to/by Linux. If Linux
> supports the particular (meta)information, tools should handle them
> transparently. Stuff like "forks" could be handled by presenting them
> as directories.
What about new features that Linux does not understand? We could
copy files with strange features intact, since the server supports
a file copy operation.
>> You'd have the server uncompress and recompress all the data too.
>
> Why does this follow? How could it be different?
The server may use a local filesystem with compression. When a client
copies data, the server must uncompress and recompress the data.
When a client sends a file copy to the server, the server can copy
the compressed data directly.
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