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

Tejun Heo [off-list ref] writes:

Greg, please disregard my earlier NACKs and commit the patches if you're
okay with them.  I'm working on cleaning it up but I don't think I'll be
able to make it in time for merge window and as Eric said getting the
functionality in place is more important at this point as it doesn't
affect user visible interface.

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.

Eric

Hello,

Eric W. Biederman wrote:

quoted

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?

Thanks.

-- 
tejun