linux-kernel - Re: [PATCH] mm: rename and document alloc_pages_exact

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Message-ID: <alpine.DEB.2.11.1507230855510.12258@east.gentwo.org>
Date:	Thu, 23 Jul 2015 09:11:53 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ia64@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	cbe-oss-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>, Greg Thelen <gthelen@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Arnd Bergmann <arnd@...db.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Cliff Whickman <cpw@....com>,
	Robin Holt <robinmholt@...il.com>
Subject: Re: [PATCH] mm: rename and document alloc_pages_exact_node

On Wed, 22 Jul 2015, David Rientjes wrote:

> Eek, yeah, that does look bad.  I'm not even sure the
>
> 	if (nid < 0)
> 		nid = numa_node_id();
>
> is correct; I think this should be comparing to NUMA_NO_NODE rather than
> all negative numbers, otherwise we silently ignore overflow and nobody
> ever knows.

Comparing to NUMA_NO_NODE would be better. Also use numa_mem_id() instead
to support memoryless nodes better?

> The only possible downside would be existing users of
> alloc_pages_node() that are calling it with an offline node.  Since it's a
> VM_BUG_ON() that would catch that, I think it should be changed to a
> VM_WARN_ON() and eventually fixed up because it's nonsensical.
> VM_BUG_ON() here should be avoided.

The offline node thing could be addresses by using numa_mem_id()?

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