get rid of useless dget_parent() in btrfs rename() and link()

->d_parent is locked and stable there...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/btrfs/inode.c

@@ -4766,11 +4766,10 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 	if (err) {
 		drop_inode = 1;
 	} else {
-		struct dentry *parent = dget_parent(dentry);
+		struct dentry *parent = dentry->d_parent;
 		err = btrfs_update_inode(trans, root, inode);
 		BUG_ON(err);
 		btrfs_log_new_name(trans, inode, NULL, parent);
-		dput(parent);
 	}
 
 	nr = trans->blocks_used;
@@ -7062,9 +7061,8 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	BUG_ON(ret);
 
 	if (old_ino != BTRFS_FIRST_FREE_OBJECTID) {
-		struct dentry *parent = dget_parent(new_dentry);
+		struct dentry *parent = new_dentry->d_parent;
 		btrfs_log_new_name(trans, old_inode, old_dir, parent);
-		dput(parent);
 		btrfs_end_log_trans(root);
 	}
 out_fail: