Re: Disaster!

>
> Tom Lane wrote:
> > I said:
> > > If there wasn't disk space enough to hold the clog page, the checkpoint
> > > attempt should have failed. So it may be that allowing a short read in
> > > slru.c would be patching the symptom of a bug that is really elsewhere.
> >
> > After more staring at the code, I have a theory. SlruPhysicalWritePage
> > and SlruPhysicalReadPage are coded on the assumption that close() can
> > never return any interesting failure. However, it now occurs to me that
> > there are some filesystem implementations wherein ENOSPC could be
> > returned at close() rather than the preceding write(). (For instance,
> > the HPUX man page for close() states that this never happens on local
> > filesystems but can happen on NFS.) So it'd be possible for
> > SlruPhysicalWritePage to think it had successfully written a page when
> > it hadn't. This would allow a checkpoint to complete :-(
> >
> > Chris, what's your platform exactly, and what kind of filesystem are
> > you storing pg_clog on?
>
> We already have a TODO on fclose():
>
> * Add checks for fclose() failure
>
Tom was referring to close(), not fclose().
I once had an awful time searching for a memory leak caused
by a typo using close instead of fclose.
So adding checks for both is probably a good idea.

Regards, Christoph