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Subject: Re: [tip:x86/urgent] x86-32: Restore irq stacks NUMA-aware
 allocations
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>, mingo@redhat.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org, brgerst@gmail.com, tglx@linutronix.de,
        mingo@elte.hu, linux-tip-commits@vger.kernel.org
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Date: Fri, 29 Oct 2010 22:58:03 +0200
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Le samedi 30 octobre 2010 à 00:28 +0400, Cyrill Gorcunov a écrit :
> On Fri, Oct 29, 2010 at 08:32:26PM +0200, Peter Zijlstra wrote:
> > On Fri, 2010-10-29 at 06:43 +0000, tip-bot for Eric Dumazet wrote:
> > > +       irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
> > > +                                              THREAD_FLAGS,
> > > +                                              THREAD_ORDER)); 
> > 
> > Shouldn't we be checking for a NULL return from alloc_pages_node()
> > before calling page_address() on it?
> > --
> 
>  Something like below I guess, but probably we could try to allocate
> on appropriate NUMA node first and if it fails -- via old alloc_pages
> and if it fail in turn -- then we panic.

Maybe my commit message was not clear : 

There is no need to test return from alloc_pages_node() and do the
fallback. It already done properly.

If NULL is returned, then there is no memory at all on the machine.

I tested my patch on my machine with node 1 with HighMem only, and
alloc_pages_node(1, flags, order) gave me a page from node 0.