Fix upper boundary caculation in the chunks loop in SetLastWrittenLSNForBlockRange (#229)

Author: knizhnik

src/backend/access/transam/xlog.c

@@ -6177,7 +6177,8 @@ SetLastWrittenLSNForBlockRange(XLogRecPtr lsn, RelFileNode rnode, ForkNumber for
 		BlockNumber end_bucket;   /* exclusive */
 
 		start_bucket = from / LAST_WRITTEN_LSN_CACHE_BUCKET;
-		end_bucket = (from + n_blocks + LAST_WRITTEN_LSN_CACHE_BUCKET - 1) / LAST_WRITTEN_LSN_CACHE_BUCKET;
+		end_bucket = from == REL_METADATA_PSEUDO_BLOCKNO
+			? start_bucket + 1 : (from + n_blocks + LAST_WRITTEN_LSN_CACHE_BUCKET - 1) / LAST_WRITTEN_LSN_CACHE_BUCKET;
 
 		key.rnode = rnode;
 		key.forkNum = forknum;