Re: [PATCH 25/26] get rid of mountpoint->m_count

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

On Wed, Jun 11, 2025 at 07:47:00PM +0100, Al Viro wrote:
> On Wed, Jun 11, 2025 at 01:19:43PM +0200, Christian Brauner wrote:
> 
> > This feels well-suited for a DEFINE_FREE based annotation so that
> > unpin_mountpoint() is called when the scope ends.
> 
> FWIW, I'd be more interested in having unlock_mount() treated that
> way, but I'm not sure what syntax would make sense there.
> 
> scoped_cond_guard() is not a good fit, unfortunately...

Folks, how much would you hate the following trick:

lock_mount(path, &m) returning void, and indicating error by storing
ERR_PTR(-E...) into m.path; unlock_mount(&m) doing nothing if IS_ERR(m.mp);
users turned into

	scoped_guard(lock_mount, mp)(path) {
		if (IS_ERR(mp.mp))
			return ERR_PTR(mp.mp);
		....
	}