reftable/stack: reorder swapping in the reloaded stack contents

The code flow of how we swap in the reloaded stack contents is somewhat
convoluted because we switch back and forth between swapping in
different parts of the stack.

Reorder the code to simplify it. We now first close and unlink the old
tables which do not get reused before we update the stack to point to
the new stack.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

reftable/stack.c

@@ -273,30 +273,34 @@ static int reftable_stack_reload_once(struct reftable_stack *st,
 	if (err < 0)
 		goto done;
 
-	st->readers_len = new_readers_len;
-	if (st->merged)
-		reftable_merged_table_free(st->merged);
-	if (st->readers) {
-		reftable_free(st->readers);
-	}
-	st->readers = new_readers;
-	new_readers = NULL;
-	new_readers_len = 0;
-
-	new_merged->suppress_deletions = 1;
-	st->merged = new_merged;
+	/*
+	 * Close the old, non-reused readers and proactively try to unlink
+	 * them. This is done for systems like Windows, where the underlying
+	 * file of such an open reader wouldn't have been possible to be
+	 * unlinked by the compacting process.
+	 */
 	for (i = 0; i < cur_len; i++) {
 		if (cur[i]) {
 			const char *name = reader_name(cur[i]);
 			stack_filename(&table_path, st, name);
-
 			reftable_reader_decref(cur[i]);
-
-			/* On Windows, can only unlink after closing. */
 			unlink(table_path.buf);
 		}
 	}
 
+	/* Update the stack to point to the new tables. */
+	if (st->merged)
+		reftable_merged_table_free(st->merged);
+	new_merged->suppress_deletions = 1;
+	st->merged = new_merged;
+
+	if (st->readers)
+		reftable_free(st->readers);
+	st->readers = new_readers;
+	st->readers_len = new_readers_len;
+	new_readers = NULL;
+	new_readers_len = 0;
+
 done:
 	for (i = 0; i < new_readers_len; i++)
 		reftable_reader_decref(new_readers[i]);