Re: How to handle non-local renames?

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

On Thu, Sep 28, 2006 at 12:16:31PM +0200, Miklos Szeredi wrote:
> > Simpler: if alias and our dentry share the parent, it's locked and
> > we can rename without s_vfs_rename_mutex.  If they do not, walk the
> > tree under alias, unhash all non-directories and kill all directories.
> 
> What do you mean by "killing directories"?  Unhashing the inode?
> 
> Are these OK, without holding i_mutex on alias and descendents?

Only dcache locking is needed for unhashing dentries (which is what
we do to non-directories).  For directories, we should silently
unhash inodes and make sure that all future operations on those inodes
would fail.  Up to filesystem how you do that.  Additionally, make
sure that revalidation fails on those suckers.
 
> > We keep local renames, we keep renames within directory and cross-directory
> > rename on server ends up with invalidation when client notices it.
> > 
> > We don't _care_ if lookup() is not from rename.  That's OK.
> 
> Well, there's the strange case of shared parents and lookup moving the
> source into the target, effectively completing the rename, and thus
> making rename think the source and target were equal, although in fact
> they weren't...

Which is fine, since we'll get 0, i.e. rename successful.  Tolerable,
seeing that server _is_ playing games with us.