From: Jeff King <peff@peff.net>
Date: Fri, 02 Oct 2026 23:28:34 GMT
Subject: Re: [PATCH v2 6/8] repack: track the preferred pack explicitly in MIDX write steps
Message-ID: <20261002232834.GE834759@coredump.intra.peff.net>
In-Reply-To: <a85dbcd04c7957756848e5f3102744d20b509fc4.1790827875.git.me@ttaylorr.com>

On Wed, Sep 30, 2026 at 11:11:58PM -0500, Taylor Blau wrote:

> A MIDX write step marks preferred packs in its string-list entries and
> chooses the last marked entry when executing the step. That makes the
> choice depend on list order, preventing the list from being sorted for
> membership checks.
> 
> Record the last candidate directly in the step, borrowing its name from
> the write list. This preserves preferred-pack selection while allowing
> the list to be sorted without changing that choice.

This is certainly cleaner, though it looks like the existing code works
by marking item->util and then doing a linear search for it. So wouldn't
that work even after sorting?

> @@ -719,7 +713,7 @@ static int repack_make_midx_compaction_plan(struct repack_write_midx_opts *opts,
>  
>  		item = string_list_append(&step.u.write, buf.buf);
>  		if (p->multi_pack_index || i == opts->geometry->pack_nr - 1)
> -			item->util = (void *)1; /* mark as preferred */
> +			step.preferred_pack = item->string;

I am certainly happy to see these gross casts go away, though.

-Peff