dm thin: detect metadata device resizing

Allow the dm thin pool metadata device to be extended.

Whenever a pool is resumed, detect whether the size of the metadata
device has increased, and if so, extend the metadata to use the new
space.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 0cecc37..ef8dd70 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -185,6 +185,7 @@
  * blocks would be lost.
  */
 int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);
+int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);
 
 /*
  * Flicks the underlying block manager into read only mode, so you know