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

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Message-ID: <20170530143246.GJ7969@dhcp22.suse.cz>
Date:   Tue, 30 May 2017 16:32:47 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     Gerald Schaefer <gerald.schaefer@...ibm.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [-next] memory hotplug regression

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))
-- 
Michal Hocko
SUSE Labs