vdso: don't forget to adjust vma_area_list->nr

A proxy vdso is removed from the vma_area_list list,
so vma_area_list->nr must be decremented.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
iov: Add iov_grow_page() helper

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
iov: Add iov_init() helper

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
iov: Add iovec2pagemap() helper

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
iov: Add page_server_iov to iov and back helpers

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>