netdev - Re: [PATCH net v2 3/3] esp: avoid unneeded kmap

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Date:   Mon, 11 Jan 2021 09:23:23 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>, <kuba@...nel.org>,
        "Willem de Bruijn" <willemb@...gle.com>
Subject: Re: [PATCH net v2 3/3] esp: avoid unneeded kmap_atomic call

On Sat, Jan 09, 2021 at 05:18:34PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> esp(6)_output_head uses skb_page_frag_refill to allocate a buffer for
> the esp trailer.
> 
> It accesses the page with kmap_atomic to handle highmem. But
> skb_page_frag_refill can return compound pages, of which
> kmap_atomic only maps the first underlying page.
> 
> skb_page_frag_refill does not return highmem, because flag
> __GFP_HIGHMEM is not set. ESP uses it in the same manner as TCP.
> That also does not call kmap_atomic, but directly uses page_address,
> in skb_copy_to_page_nocache. Do the same for ESP.
> 
> This issue has become easier to trigger with recent kmap local
> debugging feature CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP.
> 
> Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
> Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> Cc: Steffen Klassert <steffen.klassert@...unet.com>

As this patchset goes through the net tree:

Acked-by: Steffen Klassert <steffen.klassert@...unet.com>

Thanks!