dm thin: fix metadata dev resize detection

Fix detection of the need to resize the dm thin metadata device.

The code incorrectly tried to extend the metadata device when it
didn't need to due to a merging error with patch 24347e9 ("dm thin:
detect metadata device resizing").

device-mapper: transaction manager: couldn't open metadata space map
device-mapper: thin metadata: tm_open_with_sm failed
device-mapper: thin: aborting transaction failed
device-mapper: thin: switching pool to failure mode

Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-thin.c

···
 
 	*need_commit = false;
 
-	metadata_dev_size = get_metadata_dev_size(pool->md_dev);
+	metadata_dev_size = get_metadata_dev_size_in_blocks(pool->md_dev);
 
 	r = dm_pool_get_metadata_dev_size(pool->pmd, &sb_metadata_dev_size);
 	if (r) {
···
 	}
 
 	if (metadata_dev_size < sb_metadata_dev_size) {
-		DMERR("metadata device (%llu sectors) too small: expected %llu",
+		DMERR("metadata device (%llu blocks) too small: expected %llu",
 		      metadata_dev_size, sb_metadata_dev_size);
 		return -EINVAL;