netdev - Re: [RFC PATCH net-next 1/2] net: veth: Page pool creation error handling for existing pools only

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Message-ID: <CAKhg4tJRm4EMgUWca=c7jDuEPeJc2F3SY--oVo4qWRkfO0A=pQ@mail.gmail.com>
Date: Fri, 21 Jul 2023 19:17:26 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: Yunsheng Lin <linyunsheng@...wei.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, hawk@...nel.org, ilias.apalodimas@...aro.org, 
	daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next 1/2] net: veth: Page pool creation error
 handling for existing pools only

On Wed, Jul 19, 2023 at 8:44 PM Yunsheng Lin <linyunsheng@...wei.com> wrote:
>
> On 2023/7/19 15:29, Liang Chen wrote:
> > The failure handling procedure destroys page pools for all queues,
> > including those that haven't had their page pool created yet. this patch
> > introduces necessary adjustments to prevent potential risks and
> > inconsistency with the error handling behavior.
> >
> > Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> > ---
> >  drivers/net/veth.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > index 614f3e3efab0..509e901da41d 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -1081,8 +1081,9 @@ static int __veth_napi_enable_range(struct net_device *dev, int start, int end)
> >  err_xdp_ring:
> >       for (i--; i >= start; i--)
> >               ptr_ring_cleanup(&priv->rq[i].xdp_ring, veth_ptr_free);
> > +     i = end;
> >  err_page_pool:
> > -     for (i = start; i < end; i++) {
> > +     for (i--; i >= start; i--) {
> >               page_pool_destroy(priv->rq[i].page_pool);
> >               priv->rq[i].page_pool = NULL;
>
> There is NULL checking in page_pool_destroy(),
> priv->rq[i].page_pool is set to NULL here, and the kcalloc()
> in veth_alloc_queues() ensure it is NULL initially, maybe it
> is fine as it is?
>

Sure, it doesn't cause any real problem.

This was meant to align err_page_pool handling with the case above
(though ptr_ring_cleanup cannot take an uninitialized ring), and it
doesn't always need to loop from start to end.

Thanks,
Liang

> >       }
> >