Re: [PATCH] tracefs/eventfs: Use root and instance inodes as default ownership

Al Viro
2024-01-04T01:59:13Z

On Wed, Jan 03, 2024 at 08:32:46PM -0500, Steven Rostedt wrote:

> +static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
> +{
> + struct tracefs_inode *ti;
> + struct inode *root_inode;
> +
> + root_inode = d_inode(inode->i_sb->s_root);
> +
> + /* If parent is NULL then use root inode */
> + if (!parent)
> + return root_inode;
> +
> + /* Find the inode that is flagged as an instance or the root inode */
> + do {
> + inode = d_inode(parent);
> + if (inode == root_inode)
> + return root_inode;
> +
> + ti = get_tracefs(inode);
> +
> + if (ti->flags & TRACEFS_INSTANCE_INODE)
> + return inode;
> + } while ((parent = parent->d_parent));

*blink*

This is equivalent to
...
parent = parent->d_parent;
} while (true);

->d_parent is *never* NULL. And what the hell is that loop supposed to do,
anyway? Find the nearest ancestor tagged with TRACEFS_INSTANCE_INODE?

If root is not marked that way, I would suggest
if (!parent)
parent = inode->i_sb->s_root;
while (!IS_ROOT(parent)) {
struct tracefs_inode *ti = get_tracefs(parent->d_inode);
if (ti->flags & TRACEFS_INSTANCE_INODE)
break;
parent = parent->d_parent;
}
return parent->d_inode;