Re: Question about reference count of expectations in 2.6.14 tree

[Patrick McHardy <kaber@trash.net>]

Harald Welte wrote:
> Looking at it again, and doing some tests: The current code works,
> /proc/slabinfo shows me there is no expectation leak.
> 
> This is because the reference count is also put two times:  in
> unlink_expect, and in expectation_timed_out().  Almost all over the
> place, first unlink_expect() drops the first refcount, and
> ip_conntrack_espect_put() is called explicitly to drop the second.
> 
> So yes, one count seems to be for the timer, the second one for
> ip_conntrack_expect_list.  Two references.

Correct.

> I think it would be possible to remove the second atomic_inc() and all
> the ip_conntrack_put() that immediately follow ulink_expect() - but
> would it be worth the effort?  Isn't it an over-optimization that is
> likely to cause bugs later on?

There is one spot where it isn't possible, in find_expectation
the timer reference isn't dropped but returned to the caller.
Changing it would either require a special version of unlink_expect
or an additional atomic_inc in this function. I don't think its
worth the trouble, we do take two references so this seems the
cleanest way to me.