linux-kernel - Re: [PATCH 1/2] memory-hotplug: fix not enough check of valid zones

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Message-ID: <53FE7035.4000807@jp.fujitsu.com>
Date:	Thu, 28 Aug 2014 08:56:37 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Zhang Zhen <zhenzhang.zhang@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Toshi Kani <toshi.kani@...com>
CC:	<wangnan0@...wei.com>, Linux MM <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] memory-hotplug: fix not enough check of valid zones

(2014/08/27 20:16), Zhang Zhen wrote:
> As Yasuaki Ishimatsu described the check here is not enough
> if memory has hole as follows:
>
> PFN       0x00          0xd0          0xe0          0xf0
>               +-------------+-------------+-------------+
> zone type   |   Normal    |     hole    |   Normal    |
>               +-------------+-------------+-------------+
> In this case, the check can't guarantee that this is "the last
> block of memory".
> The check of ZONE_MOVABLE has the same problem.
>
> Signed-off-by: Zhang Zhen <zhenzhang.zhang@...wei.com>

Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>

Thanks,
Yasuaki Ishimatsu

> ---
>   drivers/base/memory.c | 36 ++++++------------------------------
>   1 file changed, 6 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index ccaf37c..0fc1d25 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -374,20 +374,6 @@ static ssize_t show_phys_device(struct device *dev,
>   }
>
>   #ifdef CONFIG_MEMORY_HOTREMOVE
> -static int __zones_online_to(unsigned long end_pfn,
> -				struct page *first_page, unsigned long nr_pages)
> -{
> -	struct zone *zone_next;
> -
> -	/* The mem block is the last block of memory. */
> -	if (!pfn_valid(end_pfn + 1))
> -		return 1;
> -	zone_next = page_zone(first_page + nr_pages);
> -	if (zone_idx(zone_next) == ZONE_MOVABLE)
> -		return 1;
> -	return 0;
> -}
> -
>   static ssize_t show_zones_online_to(struct device *dev,
>   				struct device_attribute *attr, char *buf)
>   {
> @@ -407,28 +393,18 @@ static ssize_t show_zones_online_to(struct device *dev,
>
>   	zone = page_zone(first_page);
>
> -#ifdef CONFIG_HIGHMEM
> -	if (zone_idx(zone) == ZONE_HIGHMEM) {
> -		if (__zones_online_to(end_pfn, first_page, nr_pages))
> +	if (zone_idx(zone) == ZONE_MOVABLE - 1) {
> +		/*The mem block is the last memoryblock of this zone.*/
> +		if (end_pfn == zone_end_pfn(zone))
>   			return sprintf(buf, "%s %s\n",
>   					zone->name, (zone + 1)->name);
>   	}
> -#else
> -	if (zone_idx(zone) == ZONE_NORMAL) {
> -		if (__zones_online_to(end_pfn, first_page, nr_pages))
> -			return sprintf(buf, "%s %s\n",
> -					zone->name, (zone + 1)->name);
> -	}
> -#endif
>
>   	if (zone_idx(zone) == ZONE_MOVABLE) {
> -		if (!pfn_valid(start_pfn - nr_pages))
> -			return sprintf(buf, "%s %s\n",
> -						zone->name, (zone - 1)->name);
> -		zone_prev = page_zone(first_page - nr_pages);
> -		if (zone_idx(zone_prev) != ZONE_MOVABLE)
> +		/*The mem block is the first memoryblock of ZONE_MOVABLE.*/
> +		if (start_pfn == zone->zone_start_pfn)
>   			return sprintf(buf, "%s %s\n",
> -						zone->name, (zone - 1)->name);
> +					zone->name, (zone - 1)->name);
>   	}
>
>   	return sprintf(buf, "%s\n", zone->name);
>


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