| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Tomas Vondra <tv(at)fuzzy(dot)cz>, Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Subject: | Re: hio.c does visibilitymap_pin()/IO while holding buffer lock |
| Date: | 2023-03-25 16:39:03 |
| Message-ID: | 20230325163903.eu67kqcqo4llhc4u@awork3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2023-03-25 14:34:25 +0100, Tomas Vondra wrote:
> On 3/25/23 03:57, Andres Freund wrote:
> > 2) Change relevant code so that we only return a valid vmbuffer if we could do
> > so without blocking / IO and, obviously, skip updating the VM if we
> > couldn't get the buffer.
> >
>
> I don't recall the exact details about the vm locking/pinning, but can't
> we just ensure we actually follow the proper locking order? I mean, this
> only deals with new pages, requested at line ~624:
>
> buffer = ReadBufferBI(relation, P_NEW, RBM_ZERO_AND_LOCK, bistate);
>
> Can't we ensure we actually lock the vm buffer too in ReadBufferBI,
> before calling ReadBufferExtended? Or am I confused and that's not
> possible for some reason?
Note that this is using P_NEW. I.e. we don't know the buffer location yet.
Greetings,
Andres Freund
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