dm: do not forward ioctls from logical volumes to the underlying device

dm: do not forward ioctls from logical volumes to the underlying device

commit ec8013beddd717d1740cfefb1a9b900deef85462 upstream.

A logical volume can map to just part of underlying physical volume.
In this case, it must be treated like a partition.

Based on a patch from Alasdair G Kergon.

Cc: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[PG: drop drivers/md/dm-flakey.c chunk; file not present in 2.6.34]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>