Re: [Bug Report + Patch] File descriptor leak when io_method=io_uring

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       not tested
Spec compliant:           not tested
Documentation:            not tested

Hi Lucas,
I reviewed v3 on Debian, kernel 6.17.13, liburing 2.14.
I reproduced the bug on unpatched master: fd count doubles from 142 to 284 after killing a backend. With the patch applied, the count stays stable. The fix works.
Build was clean, no new warnings. All 245 regression tests pass, make check-world passes, and all 39 TAP tests pass.
The code is clean and follows PostgreSQL conventions. The null guard before registering the callback is correct, the wrapper satisfies the on_shmem_exit() signature, and setting pgaio_uring_contexts to NULL after cleanup prevents a double-free.
One note for the committer: on_shmem_exit() callbacks fire in LIFO order, so this callback runs before anything registered earlier in AioShmemInit(), which is the safe direction. Worth confirming that no earlier-registered callback could invalidate pgaio_uring_contexts before this one runs.
On the v1 vs v2 design question: I favour v2. The Table AM precedent suggests PostgreSQL prefers clean interface boundaries even with a single implementor, and Andres Freund has been explicit about this in the past.
Marking as Ready for Committer.
Regards,
Lætitia