Re: [PATCH 12/15] driver core: Implement tagged directory supportfor device classes.

From: Tejun Heo
Date: Wed Jul 16 2008 - 01:50:49 EST


Eric W. Biederman wrote:
>> Eric, with the multiple superblocks, sysfs now uses inode from the
>> default sysfs_sb with dentries from other sb's. Is this okay? Are
>> there any other filesystems which do this?
> I don't know of any other filesystems where this unique challenge arises.
> /proc almost qualifies but it never needs to be modified.
> It is certainly ok to go from multiple dentries to a single inode.
> I'm trying to remember why I choose to do that. I think both because it simplifies
> the locking and keeps us more efficient in the icache.

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?


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