[PATCHv5 1/2] block: accumulate memory segment gaps per bio

[Christoph Hellwig]

On Mon, Nov 10, 2025 at 11:50:51PM -0500, Keith Busch wrote:
> Thanks for the heads up. This is in the path I'd been modifying lately,
> so sounds plausible that I introduced the bug. The information here
> should be enough for me to make progress: it looks like req->bio is NULL
> in your trace, which I did not expect would happen. But it's late here
> too, so look with fresh eyes in the morning.

req->bio should only be NULL for flush requests or passthrough requests
that do not transfer data.  None of them should end up in this path.