dm table: pass correct dev area size to device_area_is_valid

Incorrect device area lengths are being passed to device_area_is_valid().

The regression appeared in 2.6.31-rc1 through commit
754c5fc7ebb417b23601a6222a6005cc2e7f2913.

With the dm-stripe target, the size of the target (ti->len) was used
instead of the stripe_width (ti->len/#stripes).  An example of a
consequent incorrect error message is:

  device-mapper: table: 254:0: sdb too small for target

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 0d63106..655e772 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -84,7 +84,7 @@
 
 typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
 					   struct dm_dev *dev,
-					   sector_t physical_start,
+					   sector_t start, sector_t len,
 					   void *data);
 
 typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
@@ -104,7 +104,7 @@
  * Combine device limits.
  */
 int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
-			 sector_t start, void *data);
+			 sector_t start, sector_t len, void *data);
 
 struct dm_dev {
 	struct block_device *bdev;