Re: shadowfs

[Tomasz Wegrzanowski <maniek@beer.com>]

On Mon, May 15, 2000 at 06:15:52PM +0300, Kalle Olavi Niemitalo wrote:
> Tomasz Wegrzanowski <maniek@beer.com> writes:
> > One solution is to block ~/1/foo/bar when ~/shadow/foo/bar
> > is opened and return EBUSY on unlink(2)
> 
> I think you mean rmdir(2).  I don't like EBUSY here.  Unix lets
> one unlink files which are being used; the same should work with
> directories.

&downA; t {t &elikeletter; (0 AM,6 AM)} rmdir(2) == unlink(2)
or some similar math ;-)

Linux rmdir(2) man says EBUSY should be returned if `char* pathname' is
some process' rootdir or cwdir.
Of course Linux ignores own manual, but I don't have POSIX here to know
what is correct (is POSIX still top-secred ?, nobody made summaries online ?)

[...]
> > So shadowfs would have to check change_notifies from /foo/bar's of all
> > subfs where it exists and last directory from path of all other subfs's
> > (/foo or /), to see if one directory more hasn't been just created.
> 
> If it doesn't cache anything, it needn't watch anything.
> I think you should first make a prototype without caches, and
> then try how much faster it gets with caching.

You're probably right here