Re: [PATCH 4/4] odb/source-files: only reload alternates when the file has changed

[Junio C Hamano <gitster@pobox.com>]

Patrick Steinhardt <ps@pks.im> writes:

> +	if (!validity || !stat_validity_check(validity, path)) {
> +		int fd = open(path, O_RDONLY);
> +		if (fd < 0) {
> +			warn_on_fopen_errors(path);
> +			if (validity)
> +				stat_validity_clear(validity);
> +		} else {
> +			if (validity)
> +				stat_validity_update(validity, fd);
> +			if (strbuf_read(&buf, fd, 1024) < 0)
> +				warning_errno(_("unable to read alternates file '%s'"),
> +					      path);
> +			else
> +				parse_alternates(buf.buf, '\n', object_dir, out);
> +			close(fd);

When we update validity and then fail to strbuf_read(), say due to a
transient I/O error or something that was caused by somebody else
mucking with our alternates list at the same time, we warn, but do
not roll back the validity update even though we failed to parse.  I
wonder if it is safer to run the validity update only after
successfully read the alternates file, and if the extra safety is
worth it?