Re: AIO v2.5

Hi,

Attached is v2.9 with the following, fairly small, changes:
- Rebased ontop of the additional committed read stream patches

- Committed the localbuf: refactorings (but not the change to expand
refcounting of local buffers, that seems a bit more dependent on the rest)

- Committed the temp table test after some annoying debugging
https://postgr.es/m/w5wr26ijzp7xz2qrxkt6dzvmmn2tn6tn5fp64y6gq5iuvg43hw%40v4guo6x776dq

- Some rephrasing and moving of comments in the first two commits

- There was a small bug in the smgr reopen call I found when reviewing, the
PgAioOpData->read.fd field was referenced for both reads and writes, which
failed to fail because both read/write use a compatible struct layout.

Unless I hear otherwise, I plan to commit the first two patches fairly soon,
followed by the worker support patches a few buildfarm cycles later.

I'm sure there's a bunch of stuff worth improving in the AIO infrastructure
and I can't imagine a project of this size not having bugs. But I think it's
in a state where that's better worked out in tree, with broader exposure and
testing.

Greetings,

Andres Freund