Quoting Matthew Wilcox (2021-03-22 10:05:36)
> On Mon, Mar 22, 2021 at 09:55:50AM +0100, Antoine Tenart wrote:
> > I only had a quick look at this, but I think the issue should be fixed
> > with:
> >
> > diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> > index e16d54aabd4c..3ae3c20eb64c 100644
> > --- a/net/core/net-sysfs.c
> > +++ b/net/core/net-sysfs.c
> > @@ -1378,7 +1378,7 @@ static ssize_t xps_queue_show(struct net_device *dev, unsigned int index,
> > nr_ids = dev_maps ? dev_maps->nr_ids :
> > (type == XPS_CPUS ? nr_cpu_ids : dev->num_rx_queues);
> >
> > - mask = bitmap_zalloc(nr_ids, GFP_KERNEL);
> > + mask = bitmap_zalloc(nr_ids, GFP_ATOMIC);
> > if (!mask) {
> > rcu_read_unlock();
> > return -ENOMEM;
>
> sysfs isn't a good reason to use GFP_ATOMIC.
>
> try something like this:
>
> - mask = bitmap_zalloc(nr_ids, GFP_KERNEL);
> + mask = bitmap_zalloc(nr_ids, GFP_NOWAIT);
> if (!mask) {
> + int new_nr_ids;
> +
> rcu_read_unlock();
> - return -ENOMEM;
> + mask = bitmap_zalloc(nr_ids, GFP_KERNEL);
> + if (!mask)
> + return -ENOMEM;
> + rcu_read_lock();
> + dev_maps = rcu_dereference(dev->xps_maps[type]);
> + /* if nr_ids shrank while we slept, do not overrun array.
> + * if it increased, we just won't show the new ones
> + */
> + new_nr_ids = dev_maps ? dev_maps->nr_ids :
> + (type == XPS_CPUS ? nr_cpu_ids : dev->num_rx_queues);
> + if (new_nr_ids < nr_ids)
> + nr_ids = new_nr_ids;
Thanks for the suggestion, I'll look into that. We could also just
return -ENOMEM if the first allocation fails, retrying adds a lot of
complexity.
Antoine
