Re: [PATCH 1/6] fs: add a new remove_bdev() super operations callback

[Christian Brauner <brauner@kernel.org>]

On Thu, Jun 26, 2025 at 12:14:43PM +0200, Christoph Hellwig wrote:
> On Thu, Jun 26, 2025 at 10:38:11AM +0200, Christian Brauner wrote:
> > > +	if (sb->s_op->remove_bdev)
> > > +		sb->s_op->remove_bdev(sb, bdev, surprise);
> > > +	else if (sb->s_op->shutdown)
> > >  		sb->s_op->shutdown(sb);
> > 
> > This makes ->remove_bdev() and ->shutdown() mutually exclusive. I really
> > really dislike this pattern. It introduces the possibility that a
> > filesystem accidently implement both variants and assumes both are
> > somehow called. That can be solved by an assert at superblock initation
> > time but it's still nasty.
> > 
> > The other thing is that this just reeks of being the wrong api. We
> > should absolutely aim for the methods to not be mutually exclusive. I
> > hate that with a passion. That's just an ugly api and I want to have as
> > little of that as possible in our code.
> 
> Yes.  As I mentioned before I think we just want to transition everyone
> to the remove_bdev API.  But our life is probably easier if Qu's series
> only adds the new one so that we can do the transitions through the
> file system trees instead of needing a global API change.  Or am I
> overthinking this?

I think it's fine to do it right now. If we can avoid having
transitional stages then let's do that.