linux-kernel - Re: [-next] memory hotplug regression

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Message-Id: <20170530145501.GD4874@osiris>
Date:   Tue, 30 May 2017 16:55:01 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Gerald Schaefer <gerald.schaefer@...ibm.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [-next] memory hotplug regression

On Tue, May 30, 2017 at 04:32:47PM +0200, Michal Hocko wrote:
> On Tue 30-05-17 14:37:24, Heiko Carstens wrote:
> > On Tue, May 30, 2017 at 02:18:06PM +0200, Michal Hocko wrote:
> > > > So ZONE_DMA ends within ZONE_NORMAL. This shouldn't be possible, unless
> > > > this restriction is gone?
> > > 
> > > The patch below should help.
> > 
> > It does fix this specific problem, but introduces a new one:
> > 
> > # echo online_movable > /sys/devices/system/memory/memory16/state
> > # cat /sys/devices/system/memory/memory16/valid_zones
> > Movable
> > # echo offline > /sys/devices/system/memory/memory16/state
> > # cat /sys/devices/system/memory/memory16/valid_zones
> >           <--- no output
> > 
> > Memory block 16 is the only one I onlined and offlineto ZONE_MOVABLE.
> 
> Could you test the this on top please?
> ---
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 792c098e0e5f..a26f9f8e6365 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -937,13 +937,18 @@ void __ref move_pfn_range_to_zone(struct zone *zone,
>  	set_zone_contiguous(zone);
>  }
> 
> +/*
> + * Returns a default kernel memory zone for the given pfn range.
> + * If no kernel zone covers this pfn range it will automatically go
> + * to the ZONE_NORMAL.
> + */
>  struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
>  		unsigned long nr_pages)
>  {
>  	struct pglist_data *pgdat = NODE_DATA(nid);
>  	int zid;
> 
> -	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
> +	for (zid = 0; zid <= ZONE_NORMAL; zid++) {
>  		struct zone *zone = &pgdat->node_zones[zid];
> 
>  		if (zone_intersects(zone, start_pfn, nr_pages))

Still broken, but in different way(s):

# cat /sys/devices/system/memory/memory16/valid_zones
Normal Movable
# echo online_movable > /sys/devices/system/memory/memory16/state
# cat /sys/devices/system/memory/memory16/valid_zones
Movable
# cat /sys/devices/system/memory/memory18/valid_zones
Movable
# echo online > /sys/devices/system/memory/memory18/state
# cat /sys/devices/system/memory/memory18/valid_zones
Normal    <--- should be Movable
# cat /sys/devices/system/memory/memory17/valid_zones
          <--- no output