On Fri, Mar 4, 2022 at 8:28 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> To ensure anon_vma_name refcount does not overflow, stop anon_vma_name
> sharing when the refcount reaches REFCOUNT_MAX (2147483647), which still
> leaves INT_MAX/2 (1073741823) values before the counter reaches
> REFCOUNT_SATURATED. This should provide enough headroom for raising the
> refcounts temporarily.
This is a classic case of kref simply being the wrong type for this.
We sh ould move away from that idiotic "saturate with a warning" type,
and just codify that what the page refs do is the RightThing(tm) to
do.
I've ranted against kref for years, I hate that damn thing. It's
literally broken by design with the known leaking behavior.
Oh well. I'm taking this patch as a "fix up refcount problems", and I
guess I need to some day just extract the page_ref code into a nice
type of its own so that it's usable outside of pages.
(Others have copied the page_ref code manually, but there's no "helper
type with functions to use it", which is why people then use that
mis-designed refcount stuff).
Linus
