linux-kernel - Re: [Patch v5 5/7] acpi_memhotplug.c: don't allow to eject the memory device if it is being used

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Date:	Thu, 15 Nov 2012 18:20:27 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Wen Congyang <wency@...fujitsu.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-acpi@...r.kernel.org>, Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Toshi Kani <toshi.kani@...com>, Jiang Liu <liuj97@...il.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [Patch v5 5/7] acpi_memhotplug.c: don't allow to eject the memory
 device if it is being used

2012/11/15 15:59, Wen Congyang wrote:
> We eject the memory device even if it is in use.  It is very dangerous,
> and it will cause the kernel to be panicked.
> 
> CC: David Rientjes <rientjes@...gle.com>
> CC: Jiang Liu <liuj97@...il.com>
> CC: Len Brown <len.brown@...el.com>
> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> CC: Paul Mackerras <paulus@...ba.org>
> CC: Christoph Lameter <cl@...ux.com>
> Cc: Minchan Kim <minchan.kim@...il.com>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> CC: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> CC: Rafael J. Wysocki <rjw@...k.pl>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Signed-off-by: Wen Congyang <wency@...fujitsu.com>
> ---

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

Thanks,
Yasuaki Ishimatsu

>   drivers/acpi/acpi_memhotplug.c | 42 +++++++++++++++++++++++++++++++++---------
>   1 file changed, 33 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> index e52ad5d..f7e3007 100644
> --- a/drivers/acpi/acpi_memhotplug.c
> +++ b/drivers/acpi/acpi_memhotplug.c
> @@ -78,6 +78,7 @@ struct acpi_memory_info {
>   	unsigned short caching;	/* memory cache attribute */
>   	unsigned short write_protect;	/* memory read/write attribute */
>   	unsigned int enabled:1;
> +	unsigned int failed:1;
>   };
>   
>   struct acpi_memory_device {
> @@ -257,9 +258,23 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
>   			node = memory_add_physaddr_to_nid(info->start_addr);
>   
>   		result = add_memory(node, info->start_addr, info->length);
> -		if (result)
> +
> +		/*
> +		 * If the memory block has been used by the kernel, add_memory()
> +		 * returns -EEXIST. If add_memory() returns the other error, it
> +		 * means that this memory block is not used by the kernel.
> +		 */
> +		if (result && result != -EEXIST) {
> +			info->failed = 1;
>   			continue;
> -		info->enabled = 1;
> +		}
> +
> +		if (!result)
> +			info->enabled = 1;
> +		/*
> +		 * Add num_enable even if add_memory() returns -EEXIST, so the
> +		 * device is bound to this driver.
> +		 */
>   		num_enabled++;
>   	}
>   	if (!num_enabled) {
> @@ -280,21 +295,30 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
>   
>   static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
>   {
> -	int result;
> +	int result = 0;
>   	struct acpi_memory_info *info, *n;
>   
>   	list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
> -		if (info->enabled) {
> -			result = remove_memory(info->start_addr, info->length);
> -			if (result)
> -				return result;
> -		}
> +		if (info->failed)
> +			/* The kernel does not use this memory block */
> +			continue;
> +
> +		if (!info->enabled)
> +			/*
> +			 * The kernel uses this memory block, but it may be not
> +			 * managed by us.
> +			 */
> +			return -EBUSY;
> +
> +		result = remove_memory(info->start_addr, info->length);
> +		if (result)
> +			return result;
>   
>   		list_del(&info->list);
>   		kfree(info);
>   	}
>   
> -	return 0;
> +	return result;
>   }
>   
>   static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
> 


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