d_alloc_anon — allocate an anonymous dentry
struct dentry * d_alloc_anon (struct inode * inode);
This is similar to d_alloc_root. It is used by filesystems when creating a dentry for a given inode, often in the process of mapping a filehandle to a dentry. The returned dentry may be anonymous, or may have a full name (if the inode was already in the cache). The file system may need to make further efforts to connect this dentry into the dcache properly.
When called on a directory inode, we must ensure that the inode only ever has one dentry. If a dentry is found, that is returned instead of allocating a new one.
On successful return, the reference to the inode has been transferred
to the dentry. If NULL is returned (indicating kmalloc failure),
the reference on the inode has not been released.