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, 29 Nov 2012 21:15:44 +0800
From:	andywu106建国 <wujianguo106@...il.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>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	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 Wen Congyang <wency@...fujitsu.com>
>
> 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>
> ---
>  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;

Hi Congyang,

If a memory device booting with the system, the info->enable will equal to 0,
and can not be hot-removed in  acpi_memory_remove_memory(), right?

Thanks,
Jianguo Wu

>
> +               /*
> +                * 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)
> --
> 1.8.0
>
> --
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