pg_upgrade FAIL: can't find tablespaces

I did pg_upgrade from 8.4.17 to 9.3.5. The upgrade claimed it was
successful. However, when I start Postgres 9.3.5, I get an error message
for every one of the roughly 250 databases:

LOG: could not open tablespace directory
"pg_tblspc/16828/PG_9.3_201306121": No such file or directory
LOG: could not open tablespace directory
"pg_tblspc/16523/PG_9.3_201306121": No such file or directory
LOG: could not open tablespace directory
"pg_tblspc/16768/PG_9.3_201306121": No such file or directory
LOG: could not open tablespace directory
"pg_tblspc/16715/PG_9.3_201306121": No such file or directory
... and so forth

My Postgres looks like this

/data/postgres/main - the PGDATA directory
/data/postgres/tablespaces - where most of the data live

Urgent question: Having started 9.3 (briefly), is it possible to revert to
8.4? Or do I have to fully revert my 750GB database from a backup?

Question 2: Is there a way to get 9.3 to work? Something I did wrong with
table spaces, or a step I missed?

I pretty much ran pg_upgrade per the instructions. See complete command and
output below.

Thanks,
Craig

/usr/local/pgsql-9.3.5/bin/pg_upgrade \
--link \
--user=postgres \
--old-bindir=/usr/local/pgsql-8.4.17/bin \
--new-bindir=/usr/local/pgsql-9.3.5/bin \
--old-datadir=/data/postgres/main \
--new-datadir=/data/postgres-9.3/main \
--jobs=4

Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is a superuser ok
Checking for prepared transactions ok
Checking for reg* system OID user data types ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for large objects warning

Your installation contains large objects. The new database has an
additional large object permission table. After upgrading, you will be
given a command to populate the pg_largeobject permission table with
default permissions.

Creating dump of global objects ok
Creating dump of database schemas
ok
Checking for presence of required libraries ok
Checking database user is a superuser ok
Checking for prepared transactions ok

If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.

Performing Upgrade
------------------
Analyzing all rows in the new cluster ok
Freezing all rows on the new cluster ok
Deleting files from new pg_clog ok
Copying old pg_clog to new server ok
Setting next transaction ID for new cluster ok
Deleting files from new pg_multixact/offsets ok
Setting oldest multixact ID on new cluster ok
Resetting WAL archives ok
Setting frozenxid and minmxid counters in new cluster ok
Restoring global objects in the new cluster ok
Adding support functions to new cluster ok
Restoring database schemas in the new cluster
ok
Setting minmxid counter in new cluster ok
Removing support functions from new cluster ok
Adding ".old" suffix to old global/pg_control ok

If you want to start the old cluster, you will need to remove
the ".old" suffix from /data/postgres/main/global/pg_control.old.
Because "link" mode was used, the old cluster cannot be safely
started once the new cluster has been started.

Linking user relation files
ok
Setting next OID for new cluster ok
Sync data directory to disk ok
Creating script to analyze new cluster ok
Creating script to delete old cluster ok
Checking for large objects warning

Your installation contains large objects. The new database has an
additional large object permission table, so default permissions must be
defined for all large objects. The file
pg_largeobject.sql
when executed by psql by the database superuser will set the default
permissions.

Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade so,
once you start the new server, consider running:
analyze_new_cluster.sh

Running this script will delete the old cluster's data files:
delete_old_cluster.sh