dm space map common: fix division bug in sm_ll_find_free_block()

This division bug meant the search for free metadata space could skip
the final allocation bitmap's worth of entries. Fix affects DM thinp,
cache and era targets.

Cc: stable@vger.kernel.org
Signed-off-by: Joe Thornber <ejt@redhat.com>
Tested-by: Ming-Hung Tsai <mtsai@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/persistent-data/dm-space-map-common.c

@@ -339,6 +339,8 @@ int sm_ll_find_free_block(struct ll_disk *ll, dm_block_t begin,
 	 */
 	begin = do_div(index_begin, ll->entries_per_block);
 	end = do_div(end, ll->entries_per_block);
+	if (end == 0)
+		end = ll->entries_per_block;
 
 	for (i = index_begin; i < index_end; i++, begin = 0) {
 		struct dm_block *blk;