On Wed, Oct 12, 2022 at 03:05:33PM -0400, Taylor Blau wrote:
> When we write a MIDX bitmap after repacking, it is possible that the
> repository would be left in a state with both pack- and multi-pack
> reachability bitmaps.
>
> This can occur, for instance, if a pack that was kept (either by having
> a .keep file, or during a geometric repack in which it is not rolled up)
> has a bitmap file, and the repack wrote a multi-pack index and bitmap.
>
> When loading a reachability bitmap for the repository, the multi-pack
> one is always preferred, so the pack-based one is redundant. Let's
> remove it unconditionally, even if '-d' isn't passed, since there is no
> practical reason to keep both around. The patch below does just that.
Yeah, this is certainly a reasonable thing to be doing. I wonder if you
want to share the story of why the original midx-bitmap series did not
include this patch. It is (IMHO, at least) an interesting debugging
tale.
> builtin/repack.c | 40 +++++++++++++++++++++++++++++++++++++---
> t/t7700-repack.sh | 21 +++++++++++++++++++++
> 2 files changed, 58 insertions(+), 3 deletions(-)
The patch looks good. Two very minor comments, though I'd be happy
enough to see it merged as-is:
> +static void remove_redundant_bitmaps(struct string_list *include,
> + const char *packdir)
> +{
> + struct strbuf path = STRBUF_INIT;
> + struct string_list_item *item;
> + size_t packdir_len;
> +
> + strbuf_addstr(&path, packdir);
> + strbuf_addch(&path, '/');
> + packdir_len = path.len;
> +
> + /*
> + * Remove any pack bitmaps corresponding to packs which are now
> + * included in the MIDX.
> + */
> + for_each_string_list_item(item, include) {
> + strbuf_addstr(&path, item->string);
> + strbuf_strip_suffix(&path, ".idx");
> + strbuf_addstr(&path, ".bitmap");
> +
> + if (unlink(path.buf) && errno != ENOENT)
> + die_errno(_("could not remove stale bitmap: %s"),
> + path.buf);
We could downgrade this to a warning, since there is no downside to
retaining those files (aside from wasted space). In
remove_redundant_pack(), we call into unlink_pack_path(), which just
ignores unlink errors (though arguably it should at least warn).
> @@ -1059,10 +1088,15 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
> refs_snapshot ? get_tempfile_path(refs_snapshot) : NULL,
> show_progress, write_bitmaps > 0);
>
> + if (ret) {
> + string_list_clear(&include, 0);
> + return ret;
> + }
> +
> + if (write_bitmaps)
> + remove_redundant_bitmaps(&include, packdir);
> +
> string_list_clear(&include, 0);
> -
> - if (ret)
> - return ret;
> }
You could avoid having to repeat the string-list cleanup here by
structuring it like:
if (!ret && write_bitmaps)
remove_redundant_bitmaps(&include, packdir);
/* as before, clear string list and possibly return ret */
Since it's only one line, it's not that big a deal, but it simplifies
the flow.
It's correct either way, of course. One thing I did have to do while
reviewing this was look at this hunk in place. The context omits that
this is in the "if (write_midx)" conditional, which is of course very
important. ;)
-Peff
