block: Mark read/write in block/io.c GRAPH_RDLOCK

block: Mark read/write in block/io.c GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_driver_*() need to hold a reader lock for the graph. It doesn't add
the annotation to public functions yet.

For some places, we know that they will hold the lock, but we don't have
the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock()
with a FIXME comment. These places will be removed once everything is
properly annotated.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230203152202.49054-11-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>