Re: [patch] fs: shrink struct dentry

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

On Wed, Dec 10, 2008 at 07:00:48AM +0100, Nick Piggin wrote:
> OK, this is a new patch with updated changelog, and slightly tweaked
> change to dcookie subsystem (now we'll *never* do any more hash lookups
> on dcookie lookup, ignoring that "fast" dcookie lookups would effectively
> mean my previous version wouldn't have done any more lookups anyway).

I agree with reordering part, and I don't have too serious objections
against the rest, but...

Just what the bleeding fsck is that stuff doing to paths?

a) get two instances of fs mounted somewhere (or just have a binding, or
have two namespaces) and you'll get very funny results from dcookie -
it'll stick with vfsmount it had run into originally.  Nevermind that
it might be not reachable for you.  Or reachable for anyone, for that
matter, since the namespace it had been in might be long gone by now.

b) when is it evicted, anyway?  We are stuck with a bunch of randomly
selected pinned dentries and vfsmounts...

c) may I have whatever dcookie_user inventor had been smoking?
struct dcookie_user {
        struct list_head next;
};
with a cyclic list going through those and the only use of that list
is "is it empty?" checks.  That's one hell of a way to implement a
counter, of course, but...

Anyway, I'll put it into VFS queue.

	Al, currently one turd away from being through with audit queue for
the next merge window...