virtio: handle > 2 billion page balloon targets

If the host asks for a huge target towards_target() can overflow, and
we up oops as we try to release more pages than we have.  The simple
fix is to use a 64-bit value.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index c8a4332..0b3efc3 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -152,7 +152,7 @@ static void virtballoon_changed(struct virtio_device *vdev)
        wake_up(&vb->config_change);
 }
 
-static inline int towards_target(struct virtio_balloon *vb)
+static inline s64 towards_target(struct virtio_balloon *vb)
 {
        u32 v;
        __virtio_config_val(vb->vdev,
@@ -176,7 +176,7 @@ static int balloon(void *_vballoon)
 
        set_freezable();
        while (!kthread_should_stop()) {
-               int diff;
+               s64 diff;
 
                try_to_freeze();
                wait_event_interruptible(vb->config_change,