On Fri, Oct 02, 2015 at 04:12:12PM +0200, Jan Kara wrote:
> > + if (last_wb) {
> > + wb_put(last_wb);
> > + last_wb = NULL;
> > + }
>
> But you seem to forget to drop last_wb reference in case this was the last
> wb in the list, don't you?
You're right. Will update the patch.
> > @@ -686,6 +691,9 @@ static void cgwb_bdi_destroy(struct backing_dev_info
> > *bdi)
> > radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
> > cgwb_kill(*slot);
> >
> > + /* wb may get released after @bdi is freed, sever list head */
> > + list_del(&bdi->wb_list);
> > +
>
> But we wait for bdi->usage_cnt to drop to 0 which means there's no wb,
> don't we? What am I missing?
And I forgot that we were doing that. This isn't necessary.
> > @@ -764,15 +772,22 @@ static void cgwb_bdi_destroy(struct backing_dev_info
> > *bdi) { }
> >
> > int bdi_init(struct backing_dev_info *bdi)
> > {
> > + int ret;
> > +
> > bdi->dev = NULL;
> >
> > bdi->min_ratio = 0;
> > bdi->max_ratio = 100;
> > bdi->max_prop_frac = FPROP_FRAC_BASE;
> > INIT_LIST_HEAD(&bdi->bdi_list);
> > + INIT_LIST_HEAD(&bdi->wb_list);
> > init_waitqueue_head(&bdi->wb_waitq);
> >
> > - return cgwb_bdi_init(bdi);
> > + ret = cgwb_bdi_init(bdi);
> > +
> > + list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
>
> Won't this be more logical in cgwb_bdi_init()?
bdi->wb_list exists whether cgwb is enabled or not, so if we move this
to cgwb_bdi_init(), we'll be duplicating it in both paths.
Thanks.
--
tejun
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