New device-mapper target that can delay I/O (for testing).  Reads can be
separated from writes, redirected to different underlying devices and delayed
by differing amounts of time.
Signed-off-by: NHeinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: NMilan Broz <mbroz@redhat.com>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>