Name
d_backing_inode — 
     Get upper or lower inode we should be using
 
Synopsis
| struct inode * d_backing_inode ( | const struct dentry * upper ); | 
 
Description
   This is the helper that should be used to get at the inode that will be used
   if this dentry were to be opened as a file.  The inode may be on the upper
   dentry or it may be on a lower dentry pinned by the upper.
   
   Normal filesystems should not use this to access their own inodes.