netdev - Re: [PATCH v2] netfilter: ipset: Fix sleeping memory allocation in atomic context

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Date:	Fri, 16 Oct 2015 11:22:12 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Nikolay Borisov <n.borisov@...eground.com>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	Nikolay Borisov <kernel@...p.com>,
	David Miller <davem@...emloft.net>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	SiteGround Operations <operations@...eground.com>
Subject: Re: [PATCH v2] netfilter: ipset: Fix sleeping memory allocation in
 atomic context

On Thu, Oct 15, 2015 at 01:53:11PM -0700, Eric Dumazet wrote:
> On Thu, 2015-10-15 at 23:20 +0300, Nikolay Borisov wrote:
> 
> > While GFP_ATOMIC does indeed look the correct solution for this particular
> > case I was wondering whether something like (GFP_KERNEL & ~__GFP_WAIT)
> > wouldn't also make the cut without causing sleeping? I guess this is exactly
> > the sort of situation that Mel Gorman's patch can address
> > (marc.info/?l=linux-kernel&m=144283282101953) ?
> 
> This is not applicable here, because the caller would have to find a way
> to keep trying.
> 
> I believe one way to handle this problem (in a followup patch) would be
> to use a work queue for the gc, not a timer.
> 
> Using a timer for gc is almost always subject to big problems anyway.

Agreed, this is what we're doing in nft_hash. Thanks for feedback Eric!
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