netdev - Re: [PATCH net] sunrpc: fix UDP memory accounting

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Date:   Wed, 31 Aug 2016 13:45:51 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Benjamin Coddington <bcodding@...hat.com>
Cc:     netdev@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        "David S. Miller" <davem@...emloft.net>, linux-nfs@...r.kernel.org,
        Jan Stancek <jstancek@...hat.com>
Subject: Re: [PATCH net] sunrpc: fix UDP memory accounting

On Tue, 2016-08-30 at 12:28 -0400, Benjamin Coddington wrote:
> On 25 Aug 2016, at 12:42, Paolo Abeni wrote:
> 
> > The commit f9b2ee714c5c ("SUNRPC: Move UDP receive data path
> > into a workqueue context"), as a side effect, moved the
> > skb_free_datagram() call outside the scope of the related socket
> > lock, but UDP sockets require such lock to be held for proper
> > memory accounting.
> > Fix it by replacing skb_free_datagram() with
> > skb_free_datagram_locked().
> >
> > Fixes: f9b2ee714c5c ("SUNRPC: Move UDP receive data path into a 
> > workqueue context")
> > Reported-and-tested-by: Jan Stancek <jstancek@...hat.com>
> > Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> 
> Thanks for finding this. A similar fix in 2009 for svcsock.c was done by 
> Eric Dumazet:
> 9d410c796067 ("net: fix sk_forward_alloc corruption")
> 
> skb_free_datagram_locked() is used for all xprt types in svcsock.c, 
> should we use
> it for the xs_local_transport as well in xprtsock.c?

AFAICS a similar fix is _not_ needed for xs_local_transport(), since it
uses AF_LOCAL sockets and such family does not support protocol's memory
accounting.

Paolo