On Tue, Aug 04, 2020 at 11:39:43AM -0700, John Hubbard wrote:
> +static inline int __compound_mapcount(struct page *page)
> +{
> + page = compound_head(page);
> + return atomic_read(compound_mapcount_ptr(page)) + 1;
> +}
I'd suggest instead:
static inline int head_mapcount(struct page *head)
{
return atomic_read(compound_mapcount_ptr(head)) + 1;
}
> +static inline int dump_page_compound_mapcount(struct page *page)
> +{
> + if (WARN_ON_ONCE(!PageCompound(page)))
> + return 0;
> + return __compound_mapcount(page);
> }
And just dropping this ... it shouldn't be used outside mm/debug.c anyway.
Thinking about it, we'll get the hint later that this is not to be trusted
when the flags from the page do not include 'head'.
