Btrfs: call d_instantiate after all ops are setup

This closes races where btrfs is calling d_instantiate too soon during
inode creation.  All of the callers of btrfs_add_nondir are updated to
instantiate after the inode is fully setup in memory.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/inode.c

@@ -4590,10 +4590,6 @@ static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
 	int err = btrfs_add_link(trans, dir, inode,
 				 dentry->d_name.name, dentry->d_name.len,
 				 backref, index);
-	if (!err) {
-		d_instantiate(dentry, inode);
-		return 0;
-	}
 	if (err > 0)
 		err = -EEXIST;
 	return err;
@@ -4655,6 +4651,7 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
 	else {
 		init_special_inode(inode, inode->i_mode, rdev);
 		btrfs_update_inode(trans, root, inode);
+		d_instantiate(dentry, inode);
 	}
 out_unlock:
 	nr = trans->blocks_used;
@@ -4722,6 +4719,7 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
 		inode->i_mapping->a_ops = &btrfs_aops;
 		inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
 		BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
+		d_instantiate(dentry, inode);
 	}
 out_unlock:
 	nr = trans->blocks_used;
@@ -4779,6 +4777,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 		struct dentry *parent = dentry->d_parent;
 		err = btrfs_update_inode(trans, root, inode);
 		BUG_ON(err);
+		d_instantiate(dentry, inode);
 		btrfs_log_new_name(trans, inode, NULL, parent);
 	}
 
@@ -7245,6 +7244,8 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 		drop_inode = 1;
 
 out_unlock:
+	if (!err)
+		d_instantiate(dentry, inode);
 	nr = trans->blocks_used;
 	btrfs_end_transaction_throttle(trans, root);
 	if (drop_inode) {