btrfs: fix bitmap leak when loading free space cache on duplicate entry

If we failed to link a free space entry because there's already a
conflicting entry for the same offset, we free the free space entry but
we don't free the associated bitmap that we had just allocated before.
Fix that by freeing the bitmap before freeing the entry.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/free-space-cache.c

@@ -857,6 +857,7 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 				spin_unlock(&ctl->tree_lock);
 				btrfs_err(fs_info,
 					"Duplicate entries in free space cache, dumping");
+				kmem_cache_free(btrfs_free_space_bitmap_cachep, e->bitmap);
 				kmem_cache_free(btrfs_free_space_cachep, e);
 				goto free_cache;
 			}