linux-kernel - Re: [PATCH -mm] mm: Fix memory hotplug + sparsemem build.

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Message-ID: <20070911091516.GE6288@shadowen.org>
Date:	Tue, 11 Sep 2007 10:15:16 +0100
From:	Andy Whitcroft <apw@...dowen.org>
To:	Yasunori Goto <y-goto@...fujitsu.com>
Cc:	Paul Mundt <lethal@...ux-sh.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -mm] mm: Fix memory hotplug + sparsemem build.

On Tue, Sep 11, 2007 at 05:18:01PM +0900, Yasunori Goto wrote:
> >  	if (onlined_pages)
> > -		node_set_state(zone->node, N_HIGH_MEMORY);
> > +		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
> >  
> >  	setup_per_zone_pages_min();
> 
> Thanks Paul-san. 
> 
> I also have another issue around here.
> (Kswapd doesn't run on memory less node now. It should run when
>  the node has memory.)
> 
> I would like to merge them like following if you don't mind.
> 
> 
> Bye.
> 
> ---
> 
> Fix kswapd doesn't run when memory is added on memory-less-node.
> Fix compile error of zone->node when CONFIG_NUMA is off.
> 
> Signed-off-by: Yasunori Goto <y-goto@...fujitsu.com>
> Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
> 
> 
> ---
>  mm/memory_hotplug.c |    9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> Index: current/mm/memory_hotplug.c
> ===================================================================
> --- current.orig/mm/memory_hotplug.c	2007-09-07 18:08:07.000000000 +0900
> +++ current/mm/memory_hotplug.c	2007-09-11 17:29:19.000000000 +0900
> @@ -211,10 +211,12 @@ int online_pages(unsigned long pfn, unsi
>  		online_pages_range);
>  	zone->present_pages += onlined_pages;
>  	zone->zone_pgdat->node_present_pages += onlined_pages;
> -	if (onlined_pages)
> -		node_set_state(zone->node, N_HIGH_MEMORY);
>  
>  	setup_per_zone_pages_min();
> +	if (onlined_pages){

Nit, needs a space there before the '{'.

> +		kswapd_run(zone_to_nid(zone));
> +		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
> +	}
>  
>  	if (need_zonelists_rebuild)
>  		build_all_zonelists();
> @@ -269,9 +271,6 @@ int add_memory(int nid, u64 start, u64 s
>  		if (!pgdat)
>  			return -ENOMEM;
>  		new_pgdat = 1;
> -		ret = kswapd_run(nid);
> -		if (ret)
> -			goto error;
>  	}
>  
>  	/* call arch's memory hotadd */

The problem as I see it is that when we boot the system we start a
kswapd on all nodes with memory.  If the hot-add adds memory to a
pre-existing node with no memory we will not start one and we end up
with a node with memory and no kswapd.  Bad.

As kswapd_run is a no-op when a kswapd already exists this seems a safe
way to fix that.  Paul's ->zone conversion is obviously correct also.

Acked-by: Andy Whitcroft <apw@...dowen.org>

-apw
-
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