Subject: Re: [PATCH 2/6] reftable/stack: don't call fsync(3p) unless provided

From: Junio C Hamano <[email-masked]>
Date: Tue, 31 Mar 2026 11:09:31 -0700

Patrick Steinhardt <[email-masked]> writes:

> Users of the reftable library are expected to provide their own function
> callback in cases they want to sync(3p) data to disk via the reftable
> write options. But if no such function was provided we end up calling
> fsync(3p) directly, which may not even be available on some systems.
>
> Drop the call to fsync(3p) and rely on the callback function
> exclusively.

Hmph, reftable-backend.c seems to do

	refs->write_options.fsync = reftable_be_fsync;

in its _be_init(), so this change is a no-op in the context of our
system, so this may be _safe_, but for a caller that wanted a fsync
to happen, returning to it without doing anything may be a bit
unexpected.  I am wondering if it should be more like

	if (!opts->fsync)
		/* BUG("whoa where is your fsync callback???") */
		reutrn -1;
	return opts->fsync(fd);

instead.

> Signed-off-by: Patrick Steinhardt <[email-masked]>
> ---
>  reftable/stack.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/reftable/stack.c b/reftable/stack.c
> index 1c9f21dfe1..f9ae832e3a 100644
> --- a/reftable/stack.c
> +++ b/reftable/stack.c
> @@ -33,7 +33,7 @@ static int stack_fsync(const struct reftable_write_options *opts, int fd)
>  {
>  	if (opts->fsync)
>  		return opts->fsync(fd);
> -	return fsync(fd);
> +	return 0;
>  }
>  
>  static ssize_t reftable_write_data(int fd, const void *data, size_t size)