This useful interface is hardly mentioned anywhere in the in-tree documentation. Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de> Cc: Tejun Heo <htejun@gmail.com> Acked-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>