Re: [PATCH 1/2] kernfs: add kernfs_ops.free operation to free resources tied to the file

[Christian Brauner]

On Mon, Jun 26, 2023 at 10:31:49AM -1000, Tejun Heo wrote:
> On Mon, Jun 26, 2023 at 01:17:12PM -0700, Suren Baghdasaryan wrote:
> > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> > index 73f5c120def8..a7e404ff31bb 100644
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -273,6 +273,11 @@ struct kernfs_ops {
> >  	 */
> >  	int (*open)(struct kernfs_open_file *of);
> >  	void (*release)(struct kernfs_open_file *of);
> > +	/*
> > +	 * Free resources tied to the lifecycle of the file, like a
> > +	 * waitqueue used for polling.
> > +	 */
> > +	void (*free)(struct kernfs_open_file *of);
> 
> I think this can use a bit more commenting - ie. explain that release may be
> called earlier than the actual freeing of the file and how that can lead to
> problems. Othre than that, looks fine to me.

It seems the more natural thing to do would be to introduce a ->drain()
operation and order it before ->release(), no?