Make sure we get a directory when we look up the recovery directory.

Thanks to Christoph Hellwig for the bug report.

Based on feedback from Christoph and others, we may remove the need for this
lookup and just pass in a file descriptor from userspace instead, and/or
completely move the directory handling to userspace.  For now we're just
fixing the obvious bugs.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>