btrfs: zoned: simplify btrfs_check_meta_write_pointer

btrfs_check_meta_write_pointer() will always be called with a NULL
'cache_ret' argument.

As there's no need to check if we have a valid block_group passed in
remove these checks.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -1637,19 +1637,10 @@ bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
 	if (!btrfs_is_zoned(fs_info))
 		return true;
 
-	cache = *cache_ret;
-
-	if (cache && (eb->start < cache->start ||
-		      cache->start + cache->length <= eb->start)) {
-		btrfs_put_block_group(cache);
-		cache = NULL;
-		*cache_ret = NULL;
-	}
-
-	if (!cache)
 	cache = btrfs_lookup_block_group(fs_info, eb->start);
+	if (!cache)
+		return true;
 
-	if (cache) {
 	if (cache->meta_write_pointer != eb->start) {
 		btrfs_put_block_group(cache);
 		cache = NULL;
@@ -1659,7 +1650,6 @@ bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
 	}
 
 	*cache_ret = cache;
-	}
 
 	return ret;
 }