DM: Fix device mapper topology stacking

Make DM use bdev_stack_limits() function so that partition offsets get
taken into account when calculating alignment.  Clarify stacking
warnings.

Also remove obsolete clearing of final alignment_offset and misalignment
flag.

Signed-off-by: Martin K. Petersen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Cc: Alasdair G. Kergon <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
1 file changed