Re: AIO v2.5

Hi,

On 2025-03-29 10:48:10 -0400, Andres Freund wrote:
> Attached is v2.14:

FWIW, there was a last minute change in the test that fails in one task on CI,
due to reading across the smaller segment size configured for one of the
runs. Doesn't quite seem worth posting a new version for.

> - push the checksums stats fix

Done.

> - unless somebody sees a reason to not use LOG_SERVER_ONLY in
> "aio: Implement support for reads in smgr/md/fd", push that
>
> Besides that the only change since Noah's last review of that commit is an
> added comment.

Also done. If we want to change log level later, it's easy to do so.

I made some small changes since the version I had posted:
- I found one dangling reference to mdread() instead of mdreadv()
- I had accidentally squashed the fix to Noah's review comment about a comment
above md_readv_report() to the wrong commit (smgr/md/fd.c write support)
- PGAIO_HCB_MD_WRITEV was added in "smgr/md/fd.c read support" instead of
"smgr/md/fd.c write support"

> - push pg_aios view (depends a tiny bit on the smgr/md/fd change above)

I think I found an issue with this one - as it stands the view was viewable by
everyone. While it doesn't provide a *lot* of insight, it still seems a bit
too much for an unprivileged user to learn what part of a relation any other
user is currently reading.

There'd be two different ways to address that:
1) revoke view & function from public, grant to a limited role (presumably
pg_read_all_stats)
2) copy pg_stat_activity's approach of using something like

#define HAS_PGSTAT_PERMISSIONS(role) (has_privs_of_role(GetUserId(), ROLE_PG_READ_ALL_STATS) || has_privs_of_role(GetUserId(), role))

on a per-IO basis.

Greetings,

Andres Freund