netdev - Re: [PATCH 10/14] netvm: Set PF_MEMALLOC as appropriate during SKB processing

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Message-ID: <BANLkTi=8jx8B8fR_+Z76UoTe_jhG9G-Tyw@mail.gmail.com>
Date:	Thu, 9 Jun 2011 14:28:24 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>, Neil Brown <neilb@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 10/14] netvm: Set PF_MEMALLOC as appropriate during SKB processing

2011/6/9 Mel Gorman <mgorman@...e.de>:
> On Thu, Jun 09, 2011 at 12:21:31PM +0200, Micha? Miros?aw wrote:
>> 2011/6/9 Mel Gorman <mgorman@...e.de>:
>> [...]
>> > +/*
>> > + * Limit which protocols can use the PFMEMALLOC reserves to those that are
>> > + * expected to be used for communication with swap.
>> > + */
>> > +static bool skb_pfmemalloc_protocol(struct sk_buff *skb)
>> > +{
>> > +       switch (skb->protocol) {
>> > +       case __constant_htons(ETH_P_ARP):
>> > +       case __constant_htons(ETH_P_IP):
>> > +       case __constant_htons(ETH_P_IPV6):
>> > +       case __constant_htons(ETH_P_8021Q):
>> > +               return true;
>> > +       default:
>> > +               return false;
>> > +       }
>> > +}
>>
>> This is not needed and wrong. Whatever list there will be, it's going
>> to always miss some obscure setup (or not that obscure, like
>> ATAoverEthernet).
>>
>
> NBD is updated in the series to set the socket information
> appropriately but the same cannot be said of AoE. The necessary
> changes have been made IPv4 and IPv6 to handle pfmemalloc sockets
> but the same cannot be necessarily said for the other protocols. Yes,
> the check could be removed but leaving it there makes a clear statement
> on what scenario can be reasonably expected to work.

Ok. Then the comment before skb_pfmemalloc_protocol() is misleading.
It should say that this is a list of protocols which implement the
required special handling of PFMEMALLOC skbs.

Best Regards,
Michał Mirosław
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