Re: BUG #18259: Assertion in ExtendBufferedRelLocal() fails after no-space-left condition

Hello tender wang,

26.12.2023 19:55, tender wang write:
> I tried to analyze the issue, and I found that it might be caused by this commit:
> commit dad50f677c42de207168a3f08982ba23c9fc6720
>        bufmgr: Acquire and clean victim buffer separately
>

Thanks for looking into it!

>     ...
>
>         With debug logging added in this code within ExtendBufferedRelLocal():
>                 if (found)
>                 {
>                     BufferDesc *existing_hdr =
>         GetLocalBufferDescriptor(hresult->id);
>                     uint32      buf_state;
>
>         UnpinLocalBuffer(BufferDescriptorGetBuffer(victim_buf_hdr));
>
>                     existing_hdr = GetLocalBufferDescriptor(hresult->id);
>                     PinLocalBuffer(existing_hdr, false);
>                     buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
>
>                     buf_state = pg_atomic_read_u32(&existing_hdr->state);
>                     Assert(buf_state & BM_TAG_VALID);
>                     Assert(!(buf_state & BM_DIRTY));
>                     buf_state &= BM_VALID;
>         pg_atomic_unlocked_write_u32(&existing_hdr->state, buf_state);
>         ...
>         I see that it reached for the second INSERT (and NOSPC error) with
>         existing_hdr->state == 0x2040000, but for the third INSERT I observe
>         state == 0x0.
>

I wonder, if "buf_state &= BM_VALID" is a typo here, maybe it supposed to be
"buf_state &= ~BM_VALID" as in ExtendBufferedRelShared()...

Best regards,
Alexander