# Re: \[PATCH 12/15\] driver core: Implement tagged directory support for device classes.

- From: Eric W. Biederman \<hidden\>
- Date: 2008-07-16 06:42:27 
- List: netdev
- Page: https://ratatoskr.run/netdev/2008/07/1126002
- Thread: https://ratatoskr.run/netdev/2008/07/1126002/t.md

```text
Tejun Heo [ref] writes:

> It's a bit scary tho.  Working inode->i_dentry or dentry->d_alias
> crosses multiple sb's.  sysfs isn't too greedy about dcache/icache.
> Only open files and directories hold them and only single copy of
> sysfs_dirent is there for most nodes.  Wouldn't it be better to stay on
> the safer side and use separate inode hierarchy?

To do that I believe we would need to ensure sysfs does not use 
the inode->i_mutex lock except to keep the VFS layer out.  Allowing us
to safely change the directory structure, without holding it.

You raise a good point about inode->i_dentry and dentry->d_alias.
Generally they are used by fat like filesystems but I am starting to
see uses in generic pieces of code.  I don't see any problems today
but yes it would be good to do the refactoring to allow us to duplicate
the inodes. 

Eric

```