Re: [PATCH net-next v20 06/14] mm: page_frag: reuse existing space for 'size' and 'pfmemalloc'

[Yunsheng Lin <linyunsheng@huawei.com>]

On 2024/10/10 22:33, Alexander Duyck wrote:

...

> 
> For the decodes yes. I was referring to page_frag_encode_page.
> Basically the output from that isn't anything page frag, it is your
> encoded page type so you could probably just call it
> encoded_page_encode, or encoded_page_create or something like that.

It is kind of confusing as there is some mix of encode/encoded/decode
here, but let's be more specific if it is something like below:

static unsigned long encoded_page_create(struct page *page, unsigned int order,
					 bool pfmemalloc)
{
	BUILD_BUG_ON(PAGE_FRAG_CACHE_MAX_ORDER > PAGE_FRAG_CACHE_ORDER_MASK);
	BUILD_BUG_ON(PAGE_FRAG_CACHE_PFMEMALLOC_BIT >= PAGE_SIZE);

	return (unsigned long)page_address(page) |
		(order & PAGE_FRAG_CACHE_ORDER_MASK) |
		((unsigned long)pfmemalloc * PAGE_FRAG_CACHE_PFMEMALLOC_BIT);
}

static inline bool encoded_page_decode_pfmemalloc(unsigned long encoded_page)
{
	return !!(encoded_page & PAGE_FRAG_CACHE_PFMEMALLOC_BIT);
}

static unsigned long encoded_page_decode_order(unsigned long encoded_page)
{
	return encoded_page & PAGE_FRAG_CACHE_ORDER_MASK;
}

static void *encoded_page_decode_virt(unsigned long encoded_page)
{
	return (void *)(encoded_page & PAGE_MASK);
}

static struct page *encoded_page_decode_page(unsigned long encoded_page)
{
	return virt_to_page((void *)encoded_page);
}