Re: [PATCH 02/12] sunrpc/cache: make sure deferred requests eventually get revisited.

J. Bruce Fields
2009-08-04T15:02:54Z

On Tue, Aug 04, 2009 at 03:22:38PM +1000, NeilBrown wrote:
> While deferred requests normally get revisited quite quickly,
> it is possible for a request to remain in the deferral queue
> when the cache item is discarded. We can easily make sure that
> doesn't happen by calling cache_revisit_request just before
> the final 'put'.
>
> Also there is a small chance that a race would cause one thread to
> defer a request against a cache item while another thread is failing
> to queue and upcall for that item. So when the upcall fails,
> make sure to revisit all deferred requests.

OK, thanks--applied.

>
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>
> net/sunrpc/cache.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index d19c075..44f4516 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -221,6 +221,7 @@ int cache_check(struct cache_detail *detail,
> switch (cache_make_upcall(detail, h)) {
> case -EINVAL:
> clear_bit(CACHE_PENDING, &h->flags);
> + cache_revisit_request(h);
> if (rv == -EAGAIN) {
> set_bit(CACHE_NEGATIVE, &h->flags);
> cache_fresh_unlocked(h, detail,
> @@ -473,8 +474,10 @@ static int cache_clean(void)
> if (!ch)
> current_index ++;
> spin_unlock(&cache_list_lock);
> - if (ch)
> + if (ch) {
> + cache_revisit_request(ch);

Possibly dumb question: does dreq->item hold a reference? Assuming not:
should we zero it out on revisit? It seems like an accident waiting to
happen otherwise.

--b.

> cache_put(ch, d);
> + }
> } else
> spin_unlock(&cache_list_lock);
>
>
>