This patch adds support for a per-target dm_flush_fn method.  This is needed
to allow dm-loop to invalidate page cache mappings in response to BLKFLSBUF
ioctl commands.
Signed-off-by: NBryn Reeves <breeves@redhat.com>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>