Re: Why are we PageInit'ing buffers in RelationAddExtraBlocks()?

Hi,

So, I'd pushed the latest version. And longfin came back with an
interesting error:

ERROR:  page 135 of relation "pg_class" should be empty but is not

The only way I can currently imagine this happening is that there's a
concurrent vacuum that discovers the page is empty, enters it into the
FSM (which now isn't happening under an extension lock anymore), and
then a separate backend starts to actually use that buffer.  That seems
tight but possible.  Seems we need to re-add the
LockRelationForExtension/UnlockRelationForExtension() logic :(

Greetings,

Andres Freund