On Sat, Apr 10, 2021 at 9:16 AM Ilias Apalodimas
[off-list ref] wrote:

Hi Matthew

On Sat, Apr 10, 2021 at 04:48:24PM +0100, Matthew Wilcox wrote:

quoted

On Sat, Apr 10, 2021 at 12:37:58AM +0200, Matteo Croce wrote:

quoted

This is needed by the page_pool to avoid recycling a page not allocated
via page_pool.

Is the PageType mechanism more appropriate to your needs?  It wouldn't
be if you use page->_mapcount (ie mapping it to userspace).

Interesting!
Please keep in mind this was written ~2018 and was stale on my branches for
quite some time.  So back then I did try to use PageType, but had not free
bits.  Looking at it again though, it's cleaned up.  So yes I think this can
be much much cleaner.  Should we go and define a new PG_pagepool?

Can this page_pool be used for TCP RX zerocopy? If yes then PageType
can not be used.

There is a recent discussion [1] on memcg accounting of TCP RX
zerocopy and I am wondering if this work can somehow help in that
regard. I will take a look at the series.

[1] https://lore.kernel.org/linux-mm/20210316013003.25271-1-arjunroy.kdev@gmail.com/ (local)