2022-03-29 15:47:14

by Matthew Wilcox

Subject: Re: [PATCH 2/2] mm: fix contiguous memmap assumptions about alloc/free pages

On Tue, Mar 29, 2022 at 09:09:28PM +0800, Chen Wandun wrote:
> +#define page_nth(head, tail) (page_to_pfn(tail) - page_to_pfn(head))

Could we avoid reintroducing page_nth()? It is a terrible name.

> @@ -1213,7 +1213,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
> ret = 0;
> goto out;
> }
> - switch (page - head_page) {
> + switch (page_nth(head_page, page)) {
> case 1:
> /* the first tail page: ->mapping may be compound_mapcount() */
> if (unlikely(compound_mapcount(page))) {

This is the only place you use it. I'd suggest free_tail_pages_check()
should take 'i' as its second parameter instead of 'page + i', then
there's no need to convert back to i.

2022-03-29 17:04:02

by Chen Wandun

Subject: Re: [PATCH 2/2] mm: fix contiguous memmap assumptions about alloc/free pages

on 2022/3/29 21:08, Matthew Wilcox wrote:
> On Tue, Mar 29, 2022 at 09:09:28PM +0800, Chen Wandun wrote:
>> +#define page_nth(head, tail) (page_to_pfn(tail) - page_to_pfn(head))
> Could we avoid reintroducing page_nth()? It is a terrible name.
how about compound_index ?
>> @@ -1213,7 +1213,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
>> ret = 0;
>> goto out;
>> }
>> - switch (page - head_page) {
>> + switch (page_nth(head_page, page)) {
>> case 1:
>> /* the first tail page: ->mapping may be compound_mapcount() */
>> if (unlikely(compound_mapcount(page))) {
> This is the only place you use it. I'd suggest free_tail_pages_check()
> should take 'i' as its second parameter instead of 'page + i', then
> there's no need to convert back to i.
OK， I will send v2， but I'm not sure whether similar function like
page_nth is needed elsewhere

>
> .