commit 6984f3c3 upstream.

This reverts commit 8464dd52, which was a misapplied debugging
version of the patch, not the final patch itself.
Signed-off-by: Chris Ball <cjb@laptop.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>