[PATCH 3/3] virtio_pci: document why we defer kfree

["Michael S. Tsirkin" <mst@redhat.com>]

The reason we defer kfree until release function is because it's a
general rule for kobjects: kfree of the reference counter itself is only
legal in the release function.

Previous patch didn't make this clear, document this in code.

Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_pci_legacy.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index 4beaee3..a5486e6 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -216,6 +216,9 @@ static void virtio_pci_release_dev(struct device *_d)
 	struct virtio_device *vdev = dev_to_virtio(_d);
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 
+	/* As struct device is a kobject, it's not safe to
+	 * free the memory (including the reference counter itself)
+	 * until it's release callback. */
 	kfree(vp_dev);
 }
 
-- 
MST