netdev - Re: [PATCH net-next] bnxt_en: Add page_pool

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Date:   Tue, 9 Jul 2019 18:20:57 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Andy Gospodarek <andrew.gospodarek@...adcom.com>
Cc:     Michael Chan <michael.chan@...adcom.com>, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next] bnxt_en: Add page_pool_destroy() during RX ring
 cleanup.

Hi,

> > Add page_pool_destroy() in bnxt_free_rx_rings() during normal RX ring
> > cleanup, as Ilias has informed us that the following commit has been
> > merged:
> > 
> > 1da4bbeffe41 ("net: core: page_pool: add user refcnt and reintroduce page_pool_destroy")
> > 
> > The special error handling code to call page_pool_free() can now be
> > removed.  bnxt_free_rx_rings() will always be called during normal
> > shutdown or any error paths.
> > 
> > Fixes: 322b87ca55f2 ("bnxt_en: add page_pool support")
> > Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Cc: Andy Gospodarek <gospo@...adcom.com>
> > Signed-off-by: Michael Chan <michael.chan@...adcom.com>
> > ---
> >  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 8 ++------
> >  1 file changed, 2 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > index e9d3bd8..2b5b0ab 100644
> > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> > @@ -2500,6 +2500,7 @@ static void bnxt_free_rx_rings(struct bnxt *bp)
> >  		if (xdp_rxq_info_is_reg(&rxr->xdp_rxq))
> >  			xdp_rxq_info_unreg(&rxr->xdp_rxq);
> >  
> > +		page_pool_destroy(rxr->page_pool);
> >  		rxr->page_pool = NULL;
> >  
> >  		kfree(rxr->rx_tpa);
> > @@ -2560,19 +2561,14 @@ static int bnxt_alloc_rx_rings(struct bnxt *bp)
> >  			return rc;
> >  
> >  		rc = xdp_rxq_info_reg(&rxr->xdp_rxq, bp->dev, i);
> > -		if (rc < 0) {
> > -			page_pool_free(rxr->page_pool);
> > -			rxr->page_pool = NULL;
> > +		if (rc < 0)
> >  			return rc;
> > -		}
> >  
> >  		rc = xdp_rxq_info_reg_mem_model(&rxr->xdp_rxq,
> >  						MEM_TYPE_PAGE_POOL,
> >  						rxr->page_pool);
> >  		if (rc) {
> >  			xdp_rxq_info_unreg(&rxr->xdp_rxq);
> > -			page_pool_free(rxr->page_pool);
> > -			rxr->page_pool = NULL;
> 
> Rather than deleting these lines it would also be acceptable to do:
> 
>                 if (rc) {
>                         xdp_rxq_info_unreg(&rxr->xdp_rxq);
> -                       page_pool_free(rxr->page_pool);
> +                       page_pool_destroy(rxr->page_pool);
>                         rxr->page_pool = NULL;
>                         return rc;
>                 }
> 
> but anytime there is a failure to bnxt_alloc_rx_rings the driver will
> immediately follow it up with a call to bnxt_free_rx_rings, so
> page_pool_destroy will be called.
> 
> Thanks for pushing this out so quickly!
> 

I also can't find page_pool_release_page() or page_pool_put_page() called when
destroying the pool. Can you try to insmod -> do some traffic -> rmmod ?
If there's stale buffers that haven't been unmapped properly you'll get a
WARN_ON for them.
This part was added later on in the API when Jesper fixed in-flight packet
handling

> Acked-by: Andy Gospodarek <gospo@...adcom.com> 
> 

Thanks
/Ilias