pg_upgrade seems a tad broken

I tried to do a pg_upgrade from 9.0.x to HEAD today.  The pg_upgrade run
went through without complaint, and I could start the postmaster, but
every connection attempt fails with 

psql: FATAL:  could not read block 0 in file "base/11964/11683": read only 0 of 8192 bytes

The database OID varies depending on which database I try to connect to,
but the filenode doesn't.  In the source 9.0 database, this relfilenode
belongs to pg_largeobject_metadata.  I'm not sure whether pg_upgrade
would've preserved relfilenode numbering, so that may or may not be a
useful hint as to where the problem is.  But in any case it's busted.
        regards, tom lane