pack-bitmap-write.c: free existing bitmaps

When writing a new bitmap, the bitmap writer code attempts to read the
existing bitmap (if one is present). This is done in order to quickly
permute the bits of any bitmaps for commits which appear in the existing
bitmap, and were also selected for the new bitmap.

But since this code was added in 341fa34887 (pack-bitmap-write: use
existing bitmaps, 2020-12-08), the resources associated with opening an
existing bitmap were never released.

It's fine to ignore this, but it's bad hygiene. It will also cause a
problem for the multi-pack-index builtin, which will be responsible not
only for writing bitmaps, but also for expiring any old multi-pack
bitmaps.

If an existing bitmap was reused here, it will also be expired. That
will cause a problem on platforms which require file resources to be
closed before unlinking them, like Windows. Avoid this by ensuring we
close reused bitmaps with free_bitmap_index() before removing them.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index d374f7884b41149fbd4b45b4a7db53c99643c699..142fd0adb86e6fc19e001a6427edb177990824d6 100644 (file)
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -520,6 +520,7 @@ int bitmap_writer_build(struct packing_data *to_pack)
        clear_prio_queue(&queue);
        clear_prio_queue(&tree_queue);
        bitmap_builder_clear(&bb);
+       free_bitmap_index(old_bitmap);
        free(mapping);
 
        trace2_region_leave("pack-bitmap-write", "building_bitmaps_total",