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

From: Jörn Engel
Date: Mon May 10 2004 - 11:03:17 EST

On Sun, 9 May 2004 23:15:33 -0600, Eric W. Biederman wrote:
> Jörn Engel <joern@xxxxxxxxxxxxxxxxxxxx> writes:
> > 3 copyfile - new copyfile() system call
> >
> 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.


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
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