Date: Wed, 22 Dec 2010 18:20:22 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Haicheng Li <haicheng.li@linux.intel.com>, lethal@linux-sh.org,
        Andi Kleen <ak@linux.intel.com>,
        Shaohui Zheng <shaohui.zheng@linux.intel.com>, dave@linux.vnet.ibm.com,
        Greg KH <gregkh@suse.de>
Subject: Re: [3/7, v9] NUMA Hotplug Emulator: Add node hotplug emulation
Message-Id: <20101222182022.a5d5da8d.akpm@linux-foundation.org>
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	<20101210073242.462037866@intel.com>
	<20101222162723.72075372.akpm@linux-foundation.org>
	<alpine.DEB.2.00.1012221736110.13932@chino.kir.corp.google.com>
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On Wed, 22 Dec 2010 17:38:44 -0800 (PST) David Rientjes <rientjes@google.com> wrote:

> On Wed, 22 Dec 2010, Andrew Morton wrote:
> 
> > > Index: linux-hpe4/mm/memory_hotplug.c
> > > ===================================================================
> > > --- linux-hpe4.orig/mm/memory_hotplug.c	2010-11-30 12:40:43.757622001 +0800
> > > +++ linux-hpe4/mm/memory_hotplug.c	2010-11-30 14:02:33.877622002 +0800
> > > @@ -924,3 +924,63 @@
> > >  }
> > >  #endif /* CONFIG_MEMORY_HOTREMOVE */
> > >  EXPORT_SYMBOL_GPL(remove_memory);
> > > +
> > > +#ifdef CONFIG_DEBUG_FS
> > > +#include <linux/debugfs.h>
> > > +
> > > +static struct dentry *memhp_debug_root;
> > > +
> > > +static ssize_t add_node_store(struct file *file, const char __user *buf,
> > > +				size_t count, loff_t *ppos)
> > > +{
> > > +	nodemask_t mask;
> > 
> > NODEMASK_ALLOC()?
> > 
> 
> We traditionally haven't been using NODEMASK_ALLOC() in sysfs (or, in this 
> case, debugfs) functions because they're never deep in a call chain.  Even 
> for 4K node support, which isn't a supported config on any arch that 
> allows CONFIG_MEMORY_HOTPLUG, this would only be 512 bytes on the short 
> stack.

I bet linux-2.6.227 supports a meganode.
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