On 2021/10/10 4:15, Matthew Wilcox wrote: > On Sat, Oct 09, 2021 at 12:49:29PM -0700, John Hubbard wrote: >> On 10/9/21 02:37, Yunsheng Lin wrote: >>> Introduce __get_page() and __put_page() to operate on the >>> base page or head of a compound page for the cases when a >>> page is known to be a base page or head of a compound page. >> >> Hi, >> >> I wonder if you are aware of a much larger, 137-patch seriesto do that: >> folio/pageset [1]? >> >> The naming you are proposing here does not really improve clarity. There >> is nothing about __get_page() that makes it clear that it's meant only >> for head/base pages, while get_page() tail pages as well. And the >> well-known and widely used get_page() and put_page() get their meaning >> shifted. >> >> This area is hard to get right, and that's why there have been 15 >> versions, and a lot of contention associated with [1]. If you have an >> alternate approach, I think it would be better in its own separate >> series, with a cover letter that, at a minimum, explains how it compares >> to folios/pagesets. As I was not familiar enough with mm, so I tried the semantic of __page_frag_cache_drain(), which expects a base page or the head page of a compound page too. I suppose we may need to put a BUG_ON() to catch the case of user passing a tail page accidentally, which is a run time error and has run time overhead? And adding a new type like folio will allow the compiler to catch the error without any overhead? > > I wasn't initially sure whether network pagepools should be part of > struct folio or should be their own separate type. At this point, I Actually only a few driver are using page pool now, and others are mostly using page allocator directly, see page_frag_alloc_align() and skb_page_frag_refill(), only changing the page pool does not seems helpful here, maybe the whole network stack should be using a new type like folio, as the netstask does not need to deal with tail page directly? And it seems virt_to_page() is one of the things need handling when netstack is changed to use a new type like folio? >
