Re: [PATCH net-next v9 3/8] page_pool: access ->pp_magic through struct netmem_desc in page_pool_page_is_pp()

[Pavel Begunkov <asml.silence@gmail.com>]

On 7/14/25 20:09, Mina Almasry wrote:
> On Thu, Jul 10, 2025 at 6:14 PM Byungchul Park <byungchul@sk.com> wrote:
...>> Both the mainline code and this patch can make sense *only if* it's
>> actually a pp page.  It's unevitable until mm provides a way to identify
>> the type of page for page pool.  Thoughts?
> 
> I don't see mainline having a problem. Mainline checks that the page
> is a pp page via the magic before using any of the pp fields. This is
> because a page* can be a pp page or a non-pp page.
> 
> With netmem_desc, having a netmem_desc* should imply that the
> underlying memory is a pp page. Having a netmem_desc* that is not
> valid because the pp_magic is not correct complicates the code for no
> reason. Every user of netmem_desc has to check pp_magic before
> actually using the fields. page_to_nmdesc should just refuse to return
> a netmem_desc* if the page is not a pp page.
> 
> Also, this patch has my Reviewed-by, even though I honestly don't see
> it as acceptable and I clearly have feedback (and Pavel seems too?).

I was fine with it as a transitory solution, but there is nothing
to argue about anymore since mm already got a nice way to type
check pages and we can use that.
  > __please__, when you make significant changes to a patch, you have to
> reset the Reviewed-by tags.
> 

-- 
Pavel Begunkov