Re: [GIT PULL] ocfs2 changes for 2.6.32

Joel Becker
2009-09-14T22:16:09Z

On Mon, Sep 14, 2009 at 02:32:36PM -0700, Linus Torvalds wrote:
> On Fri, 11 Sep 2009, Joel Becker wrote:
> >
> > Linus, et al,
> > Here are the ocfs2 feature changes for 2.6.32. The big ticket
> > item is the reflinkat(2) system call and ocfs2's support for it. The
> > ocfs2 support accounts for all but a handful of the changes. The
> > remaining few patches are fixes.
>
> I _really_ want some kind of ack's for new filesystem system calls like
> this. I'm not going to pull a new 'reflink[at]()' system call just based
> on a single filesystem.

I'll get specific acks. I sent it via ocfs2.git because others
recommended I not send it upstream in June but instead wait until
I had at least one filesystem implementing it.

> Yes, there's clearly been _some_ discussion, but (a) I've not seen it
> (since it's been on 'fsdevel', which is one of those single-topic mailing
> lists that I'm totally uninterested in, since they tend to become clique
> groups) and (b) you don't even say whether the thing has been acked by
> things like the security angle etc.

Fair enough. Don't worry, the security folks were involved.
I'll get direct acks.

> I also don't understand why it's called 'reflink'. Why not 'copyfile'? We
> should not name things by implementation, we should name things by what
> they _do_. And I'm not seeing what is so 'reflink' about this that it's
> not a 'copyfile'. I also am not entirely clear on why you need the source
> name, and not - for example - an 'fd'.
>
> Are we going to add 'freflink[at]()' at some point?

It's a link(2) analogue. symlink(2) has the loosest coupling,
and reflink(2) the highest. We're not going to add freflink[at]().
It's a snap, not a copy. It can be used to implement a copy, and
copyfile() in libc can be written with reflinkat(2), but it isn't just a
copy.

Joel

--

"There is shadow under this red rock.
(Come in under the shadow of this red rock)
And I will show you something different from either
Your shadow at morning striding behind you
Or your shadow at evening rising to meet you.
I will show you fear in a handful of dust."

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127