netdev - Re: [PATCH net v2] net: let skb_orphan

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Date:   Tue, 30 Mar 2021 19:09:58 +0200
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net v2] net: let skb_orphan_partial wake-up waiters.



On 3/30/21 6:43 PM, Paolo Abeni wrote:
> Currently the mentioned helper can end-up freeing the socket wmem
> without waking-up any processes waiting for more write memory.
> 
> If the partially orphaned skb is attached to an UDP (or raw) socket,
> the lack of wake-up can hang the user-space.
> 
> Even for TCP sockets not calling the sk destructor could have bad
> effects on TSQ.
> 
> Address the issue using skb_orphan to release the sk wmem before
> setting the new sock_efree destructor. Additionally bundle the
> whole ownership update in a new helper, so that later other
> potential users could avoid duplicate code.
> 
> v1 -> v2:
>  - use skb_orphan() instead of sort of open coding it (Eric)
>  - provide an helper for the ownership change (Eric)
> 
> Fixes: f6ba8d33cfbb ("netem: fix skb_orphan_partial()")
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>

Thanks !