Re: [PATCH v2 4/6] fs: invoke group_pin_kill() during mount teardown

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Jan 09, 2026 at 11:04:49AM -0500, Chuck Lever wrote:

> Jeff mentioned to me privately that the fs_pin API may be deprecated,
> with its sole current consumer (BSD process accounting) destined for
> removal. I'm waiting for VFS maintainer review for confirmation on
> that before deciding how to address your comment. If fs_pin is indeed
> going away, building new NFSD infrastructure on top of it would be
> unwise, and we'll have to consider a shift in direction.

FWIW, fs_pin had never been a good API and experiments with using it
for core stuff had failed - we ended up with dput_to_list() and teaching
shrink lists to DTRT with mixed-fs lists instead.

TBH, I'd rather not see it growing more users.  Said that, more serious
problem is that you are mixing per-mount and per-fs things here.

Could you go over the objects you need to deal with?  What needs to be
hidden from the normal "mount busy" logics and revoked when a mount goes
away?

Opened files are obvious, but what about e.g. write count?