Re: [PATCH 0/2] pack-write,repack: prevent opening packs too early

On Tue, Aug 31 2021, Taylor Blau wrote:

This pair of patches fixes a race where the .idx is moved into place
before the .rev file, allowing the pack to be in a state where it
appears a .rev file wasn't generated.

This can cause Git to inadvertently take the slow "generate the
reverse index on-the-fly", which does not impact correctness, but is
unnecessarily slow when compared to reading the .rev file.

The race is fixed by moving the .idx into place only after all other
pack-related files have already been written. The first patch fixes
the direct `pack-objects` case, and the second patch fixes `repack`
(which also renames pack files around).

Thanks in advance for your review.

Taylor Blau (2):
  pack-write.c: rename `.idx` file into place last
  builtin/repack.c: move `.idx` files into place last

 builtin/repack.c |  2 +-
 pack-write.c     | 12 ++++++------
 2 files changed, 7 insertions(+), 7 deletions(-)

I've reviewed this to the point of coming up with my own series on top
of it, but it can be considered separately:
https://lore.kernel.org/git/cover-0.3-00000000000-20210907T193600Z-avarab@gmail.com/ (local)

The only change (if any) would be to perhaps update the commit
message(s) to note that the *.bitmap case is left, and that the promise
of "closing the race" is still subject to the vagaries of our non-use of
fsync() here, so pedantically speaking the race is still there.

But even without those suggested changes:

Reviewed-by: Ævar Arnfjörð Bjarmason <redacted>