Add proper error handling in case an error occurs while initializing
new perag structures for a mount point.  The mount structure is
restored to its previous state by deleting and freeing any perag
structures added during the call.
Signed-off-by: NDave Chinner <david@fromorbit.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>