netdev - Re: [net-next PATCH v2] netpoll: Drop budget parameter from NAPI polling call hierarchy

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Message-Id: <20150929.145732.752475022422386278.davem@davemloft.net>
Date:	Tue, 29 Sep 2015 14:57:32 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	aduyck@...antis.com
Cc:	netdev@...r.kernel.org
Subject: Re: [net-next PATCH v2] netpoll: Drop budget parameter from NAPI
 polling call hierarchy

From: Alexander Duyck <aduyck@...antis.com>
Date: Mon, 28 Sep 2015 09:16:17 -0700

> For some reason we were carrying the budget value around between the
> various calls to napi->poll.  If for example one of the drivers called had
> a bug in which it returned a non-zero value for work this could result in
> the budget value becoming negative.
> 
> Rather than carry around a value of budget that is 0 or less we can instead
> just loop through and pass 0 to each napi->poll call.  If any driver
> returns a value for work done that is non-zero then we can report that
> driver and continue rather than allowing a bad actor to make the budget
> value negative and pass that negative value to napi->poll.
> 
> Note, the only actual change here is that instead of letting budget become
> negative we are keeping it at 0 regardless of the value returned for work
> since it should not be possible for the polling routine to do any actual
> work with a budget of 0.  So if the polling routine returns a non-0 value
> we are just reporting it and continuing with a budget of 0 rather than
> letting that work value be subtracted from the budget of 0.
> 
> Signed-off-by: Alexander Duyck <aduyck@...antis.com>

Applied, thanks.
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