Re: try_break_deleg() and atomic_open()

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2026-05-12 at 08:21 +1000, NeilBrown wrote:
> Hi Jeff,
>  quick question (I hope).
> Should atomic_open() call try_break_deleg() on the directory
> when a create is pending?
> 
> This seems a bit iffy because the VFS doesn't necessarily know if a
> create will happen before it calls ->atomic_open, so it cannot know
> if it needs to break the deleg or not.

Agreed, so I'm thinking no to doing that in generic code.

> So maybe the individual ->atomic_open functions should do it?
> 

I think that's probably what has to happen:

atomic_open() is there to handle the non-trivial open cases (mostly
network and clustered filesystems). Those, in general, also require
non-trivial delegation/lease handling. I think we sort of need to leave
it to the underlying fs in those cases since the kernel doesn't have
enough info to do it.

> I'm looking at dentry_create() which calls atomic_open() is quite a
> different way to how lookup_open() calls it.  I'd like to change
> nfsd4 so it calls something a lot more like lookup_open() and in
> looking at what I would need to change, delegated_inode stood out.
> 

Understood. I wish that were a bit less klunky, but I don't see a great
way to make it so.

Cheers,
-- 
Jeff Layton <jlayton@kernel.org>