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