Re: [RFC PATCH] file as directory

[Al Viro <viro@ftp.linux.org.uk>]

On Wed, May 23, 2007 at 05:25:49PM +0200, Miklos Szeredi wrote:
> > > How will this work with copy_tree() and namespace duplication, which
> > > currently walk the tree with only namespace_sem held?
> > 
> > Easy - grab namespace_sem, grab vfsmount_lock, walk the subtree and bump
> > mnt_busy on everything (by 1 + number of non-busy children).  Then drop
> > vfsmount_lock and do as usual, dropping references in tree being copied
> > as you go.  Nothing will get attached or detached due to namespace_sem,
> > nothing will get evicted by anybody other than you since you've got all
> > that stuff pinned down.  End of story...
> 
> Right.
> 
> Do you have some code?
> 
> Should I try to code something up?

I hope to get some breathing space next week, then I'll get back to
VFS work.  I'd rather do that one myself, since it'll be a long series
of equivalent transformations - debugging such rewrite of refcounting
done as a single patch is going to be hell.  And yes, refcounting rewrite
is near the top of the list (another thing is wading through several
threads from hell and reviewing unionfs ;-/)