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

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Message-ID: <20250729005348.GB56089@system.software.com>
Date: Tue, 29 Jul 2025 09:53:48 +0900
From: Byungchul Park <byungchul@...com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: Pavel Begunkov <asml.silence@...il.com>, linux-mm@...ck.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH v2] mm, page_pool: introduce a new page type for page
 pool in page type

On Mon, Jul 28, 2025 at 11:39:52AM -0700, Mina Almasry wrote:
> 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.

I thought you wanted to explicitly initialize it in the user sides, but
seems not.  Okay, I won't include the explicit initialization from the
next.

	Byungchul

> 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