From: Andreas Dilger <adilger@clusterfs.com>

a) we don't call ext3_error() for an IO error in ext3_find_entry(), so we
   won't do the normal ext3 error handling (mark SB in error, remount-ro
   or panic if desired);
b) in empty_dir() we don't continue checking for non-empty blocks after a
   content error (ext3_check_dir_entry() calls ext3_error() already);
c) we had decided not to mark the SB in error for holes in directories to
   allow leway in the indexed-directory implementation, but this change
   incorrectly also disabled marking the SB in error for real IO errors.