[PATCH 5/5] fs: Convert struct file::f_count to refcount_long_t

[Al Viro]

On Thu, May 02, 2024 at 03:33:40PM -0700, Kees Cook wrote:
> Underflow of f_count needs to be more carefully detected than it
> currently is. The results of get_file() should be checked, but the
> first step is detection. Redefine f_count from atomic_long_t to
> refcount_long_t.

	It is used on fairly hot paths.  What's more, it's not
at all obvious what the hell would right semantics be.

NAKed-by: Al Viro <viro at zeniv.linux.org.uk>