netdev - Re: [PATCH v2] mm, page_pool: introduce a new page type for page pool in page type

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Message-ID: <CAHS8izO6t0euQcNyhxXKPbrV7BZ1MfuMjrQiqKr-Y68t5XCGaA@mail.gmail.com>
Date: Mon, 28 Jul 2025 11:39:52 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Byungchul Park <byungchul@...com>, linux-mm@...ck.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel_team@...ynix.com, harry.yoo@...cle.com, 
	ast@...nel.org, daniel@...earbox.net, davem@...emloft.net, kuba@...nel.org, 
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	linux-rdma@...r.kernel.org
Subject: Re: [PATCH v2] mm, page_pool: introduce a new page type for page pool
 in page type

On Mon, Jul 28, 2025 at 11:35 AM Pavel Begunkov <asml.silence@...il.com> wrote:
>
> On 7/28/25 06:27, Byungchul Park wrote:
> > Changes from v1:
> >       1. Rebase on linux-next.
>
> net-next is closed, looks like until August 11.
>
> >       2. Initialize net_iov->pp = NULL when allocating net_iov in
> >          net_devmem_bind_dmabuf() and io_zcrx_create_area().
> >       3. Use ->pp for net_iov to identify if it's pp rather than
> >          always consider net_iov as pp.
> >       4. Add Suggested-by: David Hildenbrand <david@...hat.com>.
>
> Oops, looks you killed my suggested-by tag now. Since it's still
> pretty much my diff spliced with David's suggestions, maybe
> Co-developed-by sounds more appropriate. Even more so goes for
> the second patch getting rid of __netmem_clear_lsb().
>
> Looks fine, just one comment below.
>
> ...> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> > index 100b75ab1e64..34634552cf74 100644
> > --- a/io_uring/zcrx.c
> > +++ b/io_uring/zcrx.c
> > @@ -444,6 +444,7 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq,
> >               area->freelist[i] = i;
> >               atomic_set(&area->user_refs[i], 0);
> >               niov->type = NET_IOV_IOURING;
> > +             niov->pp = NULL;
>
> It's zero initialised, you don't need it.
>

This may be my bad since I said we should check if it's 0 initialized.

It looks like on the devmem side as well we kvmalloc_array the niovs,
and if I'm checking through the helpers right, kvmalloc_array does
0-initialize indeed.

-- 
Thanks,
Mina