Re: [RFC 0/7] [RFC] cramfs: fake write support

[hooanon05@yahoo.co.jp]

Arnd Bergmann:
> > By the way, how do you think link(2) or rename(2)? When the source file
> > exists on the lower writable branch, do you think copy-up is the best
> > way? Or do you think all lower branches should be readonly?
> > There is an exception in aufs's branch-select policy. That is
> > link/rename case. When the source file exists on a writable branch, aufs
> > tries link/rename it on that branch in every policy. Do you think it
> > best to do it on the top branch only?
> 
> Yes, I tend to consider the union case identical to the cross-mount
> move or link, so I'd expect the kernel to return errno=EXDEV and user
> space to handle this by doing the appropriate copy/unlink as it does
> for other cases already.

Aure rename returns EXDEV when the target is a dir and it has child
entr(y|ies) on lower branhc(es). And mv(1) handles this case.
My Engilsh might be miunderstood. Do you think link(2) should return an
error when the target exists on lower writable branch?


Junjiro Okajima