centos man page for d_splice_alias

D_SPLICE_ALIAS(9)						   The Linux VFS						 D_SPLICE_ALIAS(9)

NAME
       d_splice_alias - splice a disconnected dentry into the tree if one exists

SYNOPSIS
       struct dentry * d_splice_alias(struct inode * inode, struct dentry * dentry);

ARGUMENTS
       inode
	   the inode which may have a disconnected dentry

       dentry
	   a negative dentry which we want to point to the inode.

DESCRIPTION
       If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and DCACHE_DISCONNECTED), then d_move that in place of the given
       dentry and return it, else simply d_add the inode to the dentry and return NULL.

       This is needed in the lookup routine of any filesystem that is exportable (via knfsd) so that we can build dcache paths to directories
       effectively.

       If a dentry was found and moved, then it is returned. Otherwise NULL is returned. This matches the expected return value of ->lookup.

       Cluster filesystems may call this function with a negative, hashed dentry. In that case, we know that the inode will be a regular file, and
       also this will only occur during atomic_open. So we need to check for the dentry being already hashed only in the final case.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							 D_SPLICE_ALIAS(9)