On Mon, 13 Aug 2012 11:41:23 +0300, "Michael S. Tsirkin" <m...@redhat.com>
wrote:
> On Fri, Aug 10, 2012 at 02:55:15PM -0300, Rafael Aquini wrote:
> > +/*
> > + * Populate balloon_mapping->a_ops->freepage method to help compaction on
> > + * re-inserting an isolated page into the balloon page list.
> > + */
> > +void virtballoon_putbackpage(struct page *page)
> > +{
> > + spin_lock(&pages_lock);
> > + list_add(&page->lru, &vb_ptr->pages);
> > + spin_unlock(&pages_lock);
>
> Could the following race trigger:
> migration happens while module unloading is in progress,
> module goes away between here and when the function
> returns, then code for this function gets overwritten?
> If yes we need locking external to module to prevent this.
> Maybe add a spinlock to struct address_space?
The balloon module cannot be unloaded until it has leaked all its pages,
so I think this is safe:
static void remove_common(struct virtio_balloon *vb)
{
/* There might be pages left in the balloon: free them. */
while (vb->num_pages)
leak_balloon(vb, vb->num_pages);
Cheers,
Rusty.
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