Re: [PATCH 2/8] mm: Use find_get_swap_page in memcontrol

[Matthew Wilcox]

On Wed, Aug 26, 2020 at 10:20:02AM -0400, Johannes Weiner wrote:
> On Wed, Aug 19, 2020 at 07:48:44PM +0100, Matthew Wilcox (Oracle) wrote:
> > +   return find_get_swap_page(vma->vm_file->f_mapping,
> > +                   linear_page_index(vma, addr));
> 
> The refactor makes sense to me, but the name is confusing. We're not
> looking for a swap page, we're primarily looking for a file page in
> the page cache mapping that's handed in. Only in the special case
> where it's a shmem mapping and there is a swap entry do we consult the
> auxiliary swap cache.
> 
> How about find_get_page_or_swapcache()? find_get_page_shmemswap()?
> Maybe you have a better idea. It's a fairly specialized operation that
> isn't widely used, so a longer name isn't a bad thing IMO.

Yeah, I had trouble with the naming here too.

get_page_even_from_swap()
find_get_shmem_page()

or maybe refactor the whole thing:

        struct page *page = find_get_entry(mapping, index);
        page = find_swap_page(mapping, page);

struct page *find_swap_page(struct address_space *mapping, struct page *page)
{
        swp_entry_t swp;
        struct swap_info_struct *si;

        if (!xa_is_value(page))
                return page;
        if (!shmem_mapping(mapping))
                return NULL;

        ...
}