Re: [ANNOUNCEMENT PATCH COW] proof of concept impementation of cowlinks

["Jörn Engel" <joern@wohnheim.fh-wedel.de>]

On Sun, 9 May 2004 23:15:33 -0600, Eric W. Biederman wrote:
> Jörn Engel <joern@wohnheim.fh-wedel.de> writes:
> > 3 copyfile		- new copyfile() system call
> > http://wohnheim.fh-wedel.de/~joern/cowlink/
> 
> Question about sys_copyfile.
> 
> Is the intention that a new file with completely new permissions
> be created?
> 
> Some people have wanted a copyfile that copies all of the extra
> metadata user/group/acls.
> 
> I currently see technical merit in both approaches.
> 
> Looking at the CIFS information it appears that the CopyFILE RPC
> copies the permissions.  It is not at all clear about that, and
> the fact it appears to copy permissions may simply be a specification
> bug.  Given that FAT does not really have permissions, let alone
> extended attributes it would be an easy mistake to make.
> 
> In the general case you cannot copy permissions from one file to
> another, either you don't have those permissions yourself or the
> target file system may not support them all.  Not copying
> permissions leads to a simpler implementation with the burden
> of the work left to user space.  What is not done is a loop through
> the extended attributes.

Unless someone finds a good reason to change this, I prefer to create
new permissions and not copy the acl's.  That way, I can also
copyfile() a file belonging to someone else, as long as I have read
access to it.

Jörn

-- 
Don't worry about people stealing your ideas. If your ideas are any good,
you'll have to ram them down people's throats.
-- Howard Aiken quoted by Ken Iverson quoted by Jim Horning quoted by
   Raph Levien, 1979