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  1. Fix shared memory calculation size of PgAioCtl

  1. AioCtl Shared Memory size fix

    Madhukar . <madhukarprasad@google.com> — 2025-09-15T09:31:07Z

    Hi Folks,

While reviewing AIO code, we found an issue with AioCtlShmemSize function.
The function was not accounting for io_handles which is used post shared
memory alloc in AioShmemInit. Please find a patch to account for
io_handles member of PgAioCtl.

The patch uses sizeof(PgAioCtl) instead of offsetof(PgAioCtl, io_handles)
in AioCtlShmemSize.

Thanks,
Madhukar

  2. Re: AioCtl Shared Memory size fix

    Matthias van de Meent <boekewurm+postgres@gmail.com> — 2025-09-15T12:06:03Z

    On Mon, 15 Sept 2025 at 13:33, Madhukar . <madhukarprasad@google.com> wrote:
>
> Hi Folks,
>
> While reviewing AIO code, we found an issue with AioCtlShmemSize function. The function was not accounting for io_handles which is used post shared memory alloc in AioShmemInit.

Good catch.

Presumably this was `PgAioHandle io_handles[]` at some point, but now
that it's a pointer it's a proper part of the struct's own size, and
should be treated as such for memory accounting.

> Please find a patch to account for io_handles member of PgAioCtl.
> The patch uses sizeof(PgAioCtl) instead of offsetof(PgAioCtl, io_handles) in AioCtlShmemSize.

LGTM.


Kind regards,

Matthias van de Meent
Databricks

  3. Re: AioCtl Shared Memory size fix

    Michael Paquier <michael@paquier.xyz> — 2025-09-16T06:50:20Z

    On Mon, Sep 15, 2025 at 02:06:03PM +0200, Matthias van de Meent wrote:
> Presumably this was `PgAioHandle io_handles[]` at some point, but now
> that it's a pointer it's a proper part of the struct's own size, and
> should be treated as such for memory accounting.

I would bet on a FLEXIBLE_ARRAY_MEMBER from a previous version..

>> Please find a patch to account for io_handles member of PgAioCtl.
>> The patch uses sizeof(PgAioCtl) instead of offsetof(PgAioCtl, io_handles) in AioCtlShmemSize.
> 
> LGTM.

Yep, will fix.  Thanks for the report, the patch and the review, to
both of you.
--
Michael

  4. Re: AioCtl Shared Memory size fix

    Andres Freund <andres@anarazel.de> — 2025-09-16T23:32:02Z

    Hi,

On 2025-09-16 15:50:20 +0900, Michael Paquier wrote:
> On Mon, Sep 15, 2025 at 02:06:03PM +0200, Matthias van de Meent wrote:
> > Presumably this was `PgAioHandle io_handles[]` at some point, but now
> > that it's a pointer it's a proper part of the struct's own size, and
> > should be treated as such for memory accounting.
> 
> I would bet on a FLEXIBLE_ARRAY_MEMBER from a previous version..

Indeed. I don't remember for sure why I changed it, but I think it may have
been to make the different allocations more visible in pg_shmem_allocations.


> >> Please find a patch to account for io_handles member of PgAioCtl.
> >> The patch uses sizeof(PgAioCtl) instead of offsetof(PgAioCtl, io_handles) in AioCtlShmemSize.
> > 
> > LGTM.
> 
> Yep, will fix.  Thanks for the report, the patch and the review, to
> both of you.

Thanks for finding and fixing!

Greetings,

Andres Freund