Re: AIO v2.5

Em qui., 3 de abr. de 2025 às 15:35, Andres Freund <andres(at)anarazel(dot)de>
escreveu:

> Hi,
>
> On 2025-04-03 13:46:39 -0300, Ranier Vilela wrote:
> > Em qua., 2 de abr. de 2025 às 08:58, Andres Freund <andres(at)anarazel(dot)de>
> > escreveu:
> >
> > > Hi,
> > >
> > > I've pushed fixes for 1) and 2) and am working on 3).
> > >
> > Coverity has one report about this.
> >
> > CID 1596092: (#1 of 1): Uninitialized scalar variable (UNINIT)
> > 13. uninit_use_in_call: Using uninitialized value result_one. Field
> > result_one.result is uninitialized when calling pgaio_result_report.
>
> Isn't this a rather silly thing to warn about for coverity?

Personally, I consider every warning to be important.

> The field isn't
> used in pgaio_result_report(). It can't be a particularly rare thing to
> have
> struct fields that aren't always used?
>
Always considered a risk, someone may start using it.

>
>
> > Below not is a fix, but some suggestion:
> >
> > diff --git a/src/backend/storage/buffer/bufmgr.c
> > b/src/backend/storage/buffer/bufmgr.c
> > index 1c37d7dfe2..b0f9ce452c 100644
> > --- a/src/backend/storage/buffer/bufmgr.c
> > +++ b/src/backend/storage/buffer/bufmgr.c
> > @@ -6786,6 +6786,8 @@ buffer_readv_encode_error(PgAioResult *result,
> > else
> > result->status = PGAIO_RS_WARNING;
> >
> > + result->result = 0;
> > +
>
> That'd be completely wrong - and the tests indeed fail if you do that. The
> read might succeed with a warning (e.g. due to zero_damaged_pages) in which
> case the result still carries important information about how many blocks
> were
> successfully read.
>
That's exactly why it's not a patch.

>
>
> > /*
> > * The encoding is complicated enough to warrant cross-checking it
> against
> > * the decode function.
> > @@ -6868,8 +6870,6 @@ buffer_readv_complete_one(PgAioTargetData *td,
> uint8
> > buf_off, Buffer buffer,
> > /* Check for garbage data. */
> > if (!failed)
> > {
> > - PgAioResult result_one;
> > -
> > if (!PageIsVerified((Page) bufdata, tag.blockNum, piv_flags,
> > failed_checksum))
> > {
> > @@ -6904,6 +6904,8 @@ buffer_readv_complete_one(PgAioTargetData *td,
> uint8
> > buf_off, Buffer buffer,
> > */
> > if (*buffer_invalid || *failed_checksum || *zeroed_buffer)
> > {
> > + PgAioResult result_one;
> > +
> > buffer_readv_encode_error(&result_one, is_temp,
> > *zeroed_buffer,
> > *ignored_checksum,
> >
> >
> > 1. I couldn't find the correct value to initialize the *result* field.
>
> It is not accessed in this path. I guess we can just zero-initialize
> result_one to shut up coverity.
>
Very good.

>
>
> > 2. result_one can be reduced scope.
>
> True.
>
Ok.

best regards,
Ranier Vilela