linux-kernel - Re: [PATCH v5 14/14] memory-hotplug: free node

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Date:	Wed, 26 Dec 2012 12:55:31 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Tang Chen <tangchen@...fujitsu.com>
CC:	akpm@...ux-foundation.org, rientjes@...gle.com, liuj97@...il.com,
	len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
	cl@...ux.com, minchan.kim@...il.com,
	kosaki.motohiro@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
	wujianguo@...wei.com, wency@...fujitsu.com, hpa@...or.com,
	linfeng@...fujitsu.com, laijs@...fujitsu.com, mgorman@...e.de,
	yinghai@...nel.org, x86@...nel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-acpi@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-ia64@...r.kernel.org,
	cmetcalf@...era.com, sparclinux@...r.kernel.org
Subject: Re: [PATCH v5 14/14] memory-hotplug: free node_data when a node is
 offlined

(2012/12/24 21:09), Tang Chen wrote:
> From: Wen Congyang <wency@...fujitsu.com>
> 
> We call hotadd_new_pgdat() to allocate memory to store node_data. So we
> should free it when removing a node.
> 
> Signed-off-by: Wen Congyang <wency@...fujitsu.com>

I'm sorry but is it safe to remove pgdat ? All zone cache and zonelists are
properly cleared/rebuilded in synchronous way ? and No threads are visinting
zone in vmscan.c ?

Thanks,
-Kame

> ---
>   mm/memory_hotplug.c |   20 +++++++++++++++++++-
>   1 files changed, 19 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index f8a1d2f..447fa24 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1680,9 +1680,12 @@ static int check_cpu_on_node(void *data)
>   /* offline the node if all memory sections of this node are removed */
>   static void try_offline_node(int nid)
>   {
> +	pg_data_t *pgdat = NODE_DATA(nid);
>   	unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
> -	unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
> +	unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
>   	unsigned long pfn;
> +	struct page *pgdat_page = virt_to_page(pgdat);
> +	int i;
>   
>   	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
>   		unsigned long section_nr = pfn_to_section_nr(pfn);
> @@ -1709,6 +1712,21 @@ static void try_offline_node(int nid)
>   	 */
>   	node_set_offline(nid);
>   	unregister_one_node(nid);
> +
> +	if (!PageSlab(pgdat_page) && !PageCompound(pgdat_page))
> +		/* node data is allocated from boot memory */
> +		return;
> +
> +	/* free waittable in each zone */
> +	for (i = 0; i < MAX_NR_ZONES; i++) {
> +		struct zone *zone = pgdat->node_zones + i;
> +
> +		if (zone->wait_table)
> +			vfree(zone->wait_table);
> +	}
> +
> +	arch_refresh_nodedata(nid, NULL);
> +	arch_free_nodedata(pgdat);
>   }
>   
>   int __ref remove_memory(int nid, u64 start, u64 size)
> 


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