afs: Use d_instantiate() rather than d_add() and don't d_drop()

Use d_instantiate() rather than d_add() and don't d_drop() in
afs_vnode_new_inode().  The dentry shouldn't be removed as it's not
changing its name.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/afs/dir.c

@@ -1075,8 +1075,6 @@ static void afs_vnode_new_inode(struct afs_fs_cursor *fc,
 	if (fc->ac.error < 0)
 		return;
 
-	d_drop(new_dentry);
-
 	inode = afs_iget(fc->vnode->vfs_inode.i_sb, fc->key,
 			 newfid, newstatus, newcb, fc->cbi);
 	if (IS_ERR(inode)) {
@@ -1090,7 +1088,7 @@ static void afs_vnode_new_inode(struct afs_fs_cursor *fc,
 	vnode = AFS_FS_I(inode);
 	set_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
 	afs_vnode_commit_status(fc, vnode, 0);
-	d_add(new_dentry, inode);
+	d_instantiate(new_dentry, inode);
 }
 
 /*