netdev - Re: [RFC PATCH net-next v2 1/2] net: veth: Page pool creation error handling for existing pools only

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Date: Fri, 11 Aug 2023 20:02:30 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, linyunsheng@...wei.com, ilias.apalodimas@...aro.org, 
	daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next v2 1/2] net: veth: Page pool creation error
 handling for existing pools only

On Wed, Aug 2, 2023 at 4:56 PM Jesper Dangaard Brouer <hawk@...nel.org> wrote:
>
>
>
> On 01/08/2023 08.19, 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--) {
>
> I'm not a fan of this coding style, that iterates backwards, but I can
> see you just inherited the existing style in this function.
>
> >               page_pool_destroy(priv->rq[i].page_pool);
> >               priv->rq[i].page_pool = NULL;
> >       }
>
> The page_pool_destroy() call handles(exits) if called with NULL.
> So, I don't think this incorrect walking all (start to end) can trigger
> an actual bug.
>
> Anyhow, I do think this is more correct, so you can append my ACK for
> the real submission.
>
> Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>
>

Thanks! I will separate this patch out and make a real submission,
since it's a small fix and not really coupled with the optimization
patch which still needs some further work after receiving feedback
from Yunsheng.

Thanks,
Liang