On Mon, Mar 22, 2021 at 2:26 AM Antoine Tenart <atenart@xxxxxxxxxx> wrote:
>
> 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
I agree that the retry logic is probably unneeded. In addition we
probably don't need GFP_ATOMIC as GFP_NOWAIT will probably be good
enough as the allocation can fail and just return an -ENOMEM in the
case of low memory.
Thanks.
- Alex
