Re: BM_IO_ERROR flag is lost in TerminateBufferIO due to order of operations in UnlockBufHdrExt

Hi,

On 2026-03-25 17:51:30 +0300, Yura Sokolov wrote:
> UnlockBufHdrExt does:
> 
>    buf_state |= set_bits;
>    buf_state &= ~unset_bits;
>    buf_state &= ~BM_LOCKED;
> 
> TerminateBufferIO unconditionally does:
> 
>    unset_flag_bits |= BM_IO_ERROR;
> 
> Due to this, AbortBufferIO and buffer_readv_complete_one are failed
> to set BM_IO_ERROR with call to TerminateBufferIO.
> 
> It was found with proprietary code that was triggered on
> PGAIO_RS_ERROR and made assertion on BM_IO_ERROR presence.

That's clearly not right.  Care to write a patch?  I think we should add a
test for this in src/test/modules/test_aio too. As we don't rely on things
like BM_IO_ERROR this is quite easy to not notice.

Greetings,

Andres Freund