netdev - Re: [PATCH v2 net] net_sched: prio: insure proper transactional behavior

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Message-Id: <20160615.123043.1799077853807122411.davem@davemloft.net>
Date:	Wed, 15 Jun 2016 12:30:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	xiyou.wangcong@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net] net_sched: prio: insure proper transactional
 behavior

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 13 Jun 2016 11:33:32 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Now prio_init() can return -ENOMEM, it also has to make sure
> any allocated qdiscs are freed, since the caller (qdisc_create()) wont
> call ->destroy() handler for us.
> 
> More generally, we want a transactional behavior for "tc qdisc
> change ...", so prio_tune() should not make modifications if
> any error is returned.
> 
> It means that we must validate parameters and allocate missing qdisc(s)
> before taking root qdisc lock exactly once, to not leave the prio qdisc
> in an intermediate state.
> 
> Fixes: cbdf45116478 ("net_sched: prio: properly report out of memory errors")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Cong Wang <xiyou.wangcong@...il.com>

Applied.