On Wed, Apr 15, 2020 at 01:19:15PM +0000, Luis Chamberlain wrote:
> > if (current->throttle_queue)
> > return;
> > + if (unlikely(current->flags & PF_KTHREAD))
> > + return;
> >
> > spin_lock(&swap_avail_lock);
> > plist_for_each_entry_safe(si, next, &swap_avail_heads[node],
> > avail_lists[node]) {
> > - if (si->bdev) {
> > - blkcg_schedule_throttle(bdev_get_queue(si->bdev),
> > - true);
> > - break;
> > + if (!si->bdev)
> > + continue;
> > + if (blk_get_queue(dev_get_queue(si->bdev))) {
> > + current->throttle_queue = dev_get_queue(si->bdev);
> > + current->use_memdelay = true;
> > + set_notify_resume(current);
> > }
> > + break;
> > }
> > spin_unlock(&swap_avail_lock);
> > }
>
> Sorry, its not clear to me who calls the respective blk_put_queue()
> here?
If you look at blkcg_schedule_throttle, it only puts the queue that
was in current->throttle_queue. But mem_cgroup_throttle_swaprate
exits early when current->throttle_queue is non-zero (first two lines
quote above). So when called from mem_cgroup_throttle_swaprate,
blkcg_schedule_throttle should never actually put a queue. Open
coding the few relevant lines from blkcg_schedule_throttle in
mem_cgroup_throttle_swaprate makes that obvious.
