On 2023/10/17 23:13, Jakub Kicinski wrote: > On Tue, 17 Oct 2023 15:56:48 +0800 Yunsheng Lin wrote: >>> And I can't figure out now what the "cache" in the name is referring to. >>> Looks like these are just convenience wrappers which return VA instead >>> of struct page.. >> >> Yes, it is corresponding to some API like napi_alloc_frag() returning va >> instead of 'struct page' mentioned in patch 5. >> >> Anyway, naming is hard, any suggestion for a better naming is always >> welcomed:) > > I'd just throw a _va (for virtual address) at the end. And not really _va seems fine:) > mention it in the documentation. Plus the kdoc of the function should > say that this is just a thin wrapper around other page pool APIs, and > it's safe to mix it with other page pool APIs? I am not sure I understand what do 'safe' and 'mix' mean here. For 'safe' part, I suppose you mean if there is a va accociated with a 'struct page' without calling some API like kmap()? For that, I suppose it is safe when the driver is calling page_pool API without the __GFP_HIGHMEM flag. Maybe we should mention that in the kdoc and give a warning if page_pool_*alloc_va() is called with the __GFP_HIGHMEM flag? For the 'mix', I suppose you mean the below: 1. Allocate a page with the page_pool_*alloc_va() API and free a page with page_pool_free() API. 2. Allocate a page with the page_pool_*alloc() API and free a page with page_pool_free_va() API. For 1, it seems it is ok as some virt_to_head_page() and page_address() call between va and 'struct page' does not seem to change anything if we have enforce page_pool_*alloc_va() to be called without the __GFP_HIGHMEM flag. For 2, If the va is returned from page_address() which the allocation API is called without __GFP_HIGHMEM flag. If not, the va is from kmap*()? which means we may be calling page_pool_free_va() before kunmap*()? Is that possible? > . >
