On 11/6/18 6:30 AM, Aaron Lu wrote:
> We have multiple places of freeing a page, most of them doing similar
> things and a common function can be used to reduce code duplicate.
>
> It also avoids bug fixed in one function but left in another.
>
> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
I assume there's no arch that would run page_ref_sub_and_test(1) slower
than put_page_testzero(), for the critical __free_pages() case?
> ---
> v2: move comments close to code as suggested by Dave.
>
> mm/page_alloc.c | 36 ++++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 20 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 91a9a6af41a2..4faf6b7bf225 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4425,9 +4425,17 @@ unsigned long get_zeroed_page(gfp_t gfp_mask)
> }
> EXPORT_SYMBOL(get_zeroed_page);
>
> -void __free_pages(struct page *page, unsigned int order)
> +static inline void free_the_page(struct page *page, unsigned int order, int nr)
> {
> - if (put_page_testzero(page)) {
> + VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
> +
> + /*
> + * Free a page by reducing its ref count by @nr.
> + * If its refcount reaches 0, then according to its order:
> + * order0: send to PCP;
> + * high order: directly send to Buddy.
> + */
> + if (page_ref_sub_and_test(page, nr)) {
> if (order == 0)
> free_unref_page(page);
> else
> @@ -4435,6 +4443,10 @@ void __free_pages(struct page *page, unsigned int order)
> }
> }
>
> +void __free_pages(struct page *page, unsigned int order)
> +{
> + free_the_page(page, order, 1);
> +}
> EXPORT_SYMBOL(__free_pages);
>
> void free_pages(unsigned long addr, unsigned int order)
> @@ -4481,16 +4493,7 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
>
> void __page_frag_cache_drain(struct page *page, unsigned int count)
> {
> - VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
> -
> - if (page_ref_sub_and_test(page, count)) {
> - unsigned int order = compound_order(page);
> -
> - if (order == 0)
> - free_unref_page(page);
> - else
> - __free_pages_ok(page, order);
> - }
> + free_the_page(page, compound_order(page), count);
> }
> EXPORT_SYMBOL(__page_frag_cache_drain);
>
> @@ -4555,14 +4558,7 @@ void page_frag_free(void *addr)
> {
> struct page *page = virt_to_head_page(addr);
>
> - if (unlikely(put_page_testzero(page))) {
> - unsigned int order = compound_order(page);
> -
> - if (order == 0)
> - free_unref_page(page);
> - else
> - __free_pages_ok(page, order);
> - }
> + free_the_page(page, compound_order(page), 1);
> }
> EXPORT_SYMBOL(page_frag_free);
>
>
