[dm-devel] Topology fixes

["Martin K. Petersen" <martin petersen oracle com>]

These two patches fix several block I/O topology stacking issues.

The first patch corrects an error in calculating partition
offsets.  It should go into stable as well as .33.

The second patch is a revamp of the stacking algorithm for both
data and discard. 2.6.33 only.

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Martin K. Petersen      Oracle Linux Engineering