Re: [PATCH 0/3] commit-graph: fix corruption during generation v2 upgrade

> This brief series resolves a bug where a commit-graph would become
> corrupt when upgrading from generation number v1 to v2, as originally
> reported in [1].
>
> Some speculation occurred as to what might be causing that bug in the
> thread beginning at [1], until the problem was explained in more detail
> by Will Chandler in [2].
>
> The crux of the issue, as is described in [2] and [3], is that the
> commit_graph_data slab is reused for read and write operations involving
> the commit-graph, leading to situations where data computed in
> preparation of a write is clobbered by a read of existing data.
>
> The first patch demonstrates the issue, and the second patch prepares to
> fix it by introducing a helper function. The crux of the issue is
> described and fixed in the third patch.
>
> [1]: https://lore.kernel.org/git/YqD5dgalb9EPnz85@coredump.intra.peff.net/
> [2]: https://lore.kernel.org/git/DD88D523-0ECA-4474-9AA5-1D4A431E532A@wfchandler.org/
> [3]: https://lore.kernel.org/git/YsS7H4i5DqUZVQ5i@nand.local/