On Wed, 22 Sep 2010 14:31:54 -0400
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> On Wed, Sep 22, 2010 at 12:55:07PM +1000, NeilBrown wrote:
> > We limit the number of 'defer' requests to DFR_MAX.
> >
> > The imposition of this limit is spread about a bit - sometime we don't
> > add new things to the list, sometimes we remove old things.
> >
> > Also it is currently applied to requests which we are 'waiting' for
> > rather than 'deferring'. This doesn't seem ideal as 'waiting'
> > requests are naturally limited by the number of threads.
> >
> > So gather the DFR_MAX handling code to one place and only apply it to
> > requests that are actually being deferred.
> >
> > This means that not all 'cache_deferred_req' structures go on the
> > 'cache_defer_list, so we need to be careful when removing things.
>
> The idea sounds OK.
>
> > +static void cache_limit_defers(struct cache_deferred_req *dreq)
> > +{
> > + /* Add 'dreq' to the list of deferred requests and make sure
> > + * we don't exceed the limit of allowed deferred requests.
> > + */
> > + struct cache_deferred_req *discard = NULL;
> > +
> > + spin_lock(&cache_defer_lock);
> > + if (!list_empty(&dreq->recent) ||
> > + hlist_unhashed(&dreq->hash)) {
> > + /* Must have lost a race, maybe cache_revisit_request is
> > + * already processing this. In any case, there is nothing for
> > + * us to do.
> > + */
> > + spin_unlock(&cache_defer_lock);
>
> Did you mean to return here?
>
Yes :-(
Thanks,
NeilBrown
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