tree db07ef3ecc00f83d3d9b854929a4cb13def456a7
parent c804cdecea418c067ee7359d62139b2b3c8cec39
author NeilBrown <neilb@suse.de> 1337556513 +1000
committer NeilBrown <neilb@suse.de> 1337556513 +1000

md/raid10: Introduce 'prev' geometry to support reshape.

When RAID10 supports reshape it will need a 'previous' and a 'current'
geometry, so introduce that here.
Use the 'prev' geometry when before the reshape_position, and the
current 'geo' when beyond it.  At other times, use both as
appropriate.

For now, both are identical (And reshape_position is never set).

When we use the 'prev' geometry, we must use the old data_offset.
When we use the current (And a reshape is happening) we must use
the new_data_offset.

Signed-off-by: NeilBrown <neilb@suse.de>