in which case eviction will be
handled by the close side) or we'll see the effect of close and do
eviction ourselves.  Note that even though it's read-only access,
we do need ->file_lock here - rcu_read_lock() won't be enough to
order the things.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
~`±q–*x