Re: Extending page pinning into fs/direct-io.c

From: David Howells
Date: Thu May 25 2023 - 13:16:10 EST

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> So I suspect we should add that
> is_zero_pfn(page_to_pfn(page))
> as a helper inline function rather than write it out even more times
> (that "is this 'struct page' a zero page" pattern already exists in
> /proc and a few other places.
> is_longterm_pinnable_page() already has it, so adding it as a helper
> there in <linux/mm.h> is probably a good idea.

I just added:

static inline bool IS_ZERO_PAGE(const struct page *page)
return is_zero_pfn(page_to_pfn(page));

static inline bool IS_ZERO_FOLIO(const struct folio *folio)
return is_zero_pfn(page_to_pfn((const struct page *)folio));

to include/linux/pgtable.h. It doesn't seem I can add it to mm.h as an inline