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From:   Shakeel Butt <shakeelb@google.com>
Date:   Sat, 10 Apr 2021 10:42:30 -0700
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Subject: Re: [PATCH net-next v3 2/5] mm: add a signature in struct page
To:     Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc:     Matthew Wilcox <willy@infradead.org>,
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On Sat, Apr 10, 2021 at 9:16 AM Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> Hi Matthew
>
> On Sat, Apr 10, 2021 at 04:48:24PM +0100, Matthew Wilcox wrote:
> > On Sat, Apr 10, 2021 at 12:37:58AM +0200, Matteo Croce wrote:
> > > 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/