Re: [patch 03/15] cgroup: dont call vfs_mkdir

[Christoph Hellwig <hch@infradead.org>]

On Mon, May 05, 2008 at 02:32:22PM +0200, Miklos Szeredi wrote:
> > Looks correct but I don't think it's a good idea.  Spreading more logic
> > into filesystems without a good reason is rarely a good idea.
> 
> (Thanks for the review, Christoph)
> 
> Agreed completely, but vfs_* aren't for filesystems to call, rather
> for entities calling _into_ filesystems from the outside.  This is
> actually a very rare thing, so adding some extra logic for the sake of
> cleanliness should be OK.
> 
> Now it can be argued, that cgroup_clone() is calling into the
> filesystem from the outside.  But it's not really doing that, rather
> it's making an internal modification to a specific filesystem,
> triggered by some external action.

I don't think that matters. We're not about overly strict layering, and
especialy this kind where you call into a higher layer to get back into
the lower one is not harmful at all.  For cgroup it's only a small
duplication, but e.g. I don't really like all the duplications in the
reiserfs case.  Unless we have a very good reason why the useage of the
vfs_ function should go away from the filesystem code I don't think
we want this.