linux-kernel - Re: [RFC PATCH v3 2/3] acpi_memhotplug: Add prepare

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Date:	Sun, 25 Nov 2012 00:23:47 +0800
From:	Wen Congyang <wencongyang@...il.com>
To:	Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>
CC:	linux-acpi@...r.kernel.org, isimatu.yasuaki@...fujitsu.com,
	wency@...fujitsu.com, rjw@...k.pl, lenb@...nel.org,
	toshi.kani@...com, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v3 2/3] acpi_memhotplug: Add prepare_remove operation

At 2012/11/24 1:50, Vasilis Liaskovitis Wrote:
> Offlining and removal of memory is now done in the prepare_remove callback,
> not in the remove callback.
> 
> The prepare_remove callback will be called when trying to remove a memory device
> with the following ways:
> 
> 1. send eject request by SCI
> 2. echo 1>/sys/bus/pci/devices/PNP0C80:XX/eject
> 
> Note that unbinding the acpi driver from a memory device with:
> echo "PNP0C80:XX">  /sys/bus/acpi/drivers/acpi_memhotplug/unbind
> 
> will no longer try to remove the memory. This is in compliance with normal
> unbind driver core semantics, see the discussion in v2 of this patchset:
> https://lkml.org/lkml/2012/11/16/649

If we don't remove it when unbinding it, it may cause kernel panicked.

I have explained in another mail.

Thanks
Wen Congyang

> 
> After a successful unbind of the driver:
> - OSPM ejects of the memory device cannot proceed, as acpi_eject_store will
> return -ENODEV on missing driver.
> - SCI ejects of the memory device also cannot proceed, as they will also get
> a "driver data is NULL" error.
> So the memory can continue to be used safely after unbind.
> 
> Signed-off-by: Vasilis Liaskovitis<vasilis.liaskovitis@...fitbricks.com>
> ---
>   drivers/acpi/acpi_memhotplug.c |   18 ++++++++++++++++--
>   1 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> index eb30e5a..d0cfbd9 100644
> --- a/drivers/acpi/acpi_memhotplug.c
> +++ b/drivers/acpi/acpi_memhotplug.c
> @@ -55,6 +55,7 @@ MODULE_LICENSE("GPL");
> 
>   static int acpi_memory_device_add(struct acpi_device *device);
>   static int acpi_memory_device_remove(struct acpi_device *device, int type);
> +static int acpi_memory_device_prepare_remove(struct acpi_device *device);
> 
>   static const struct acpi_device_id memory_device_ids[] = {
>   	{ACPI_MEMORY_DEVICE_HID, 0},
> @@ -69,6 +70,7 @@ static struct acpi_driver acpi_memory_device_driver = {
>   	.ops = {
>   		.add = acpi_memory_device_add,
>   		.remove = acpi_memory_device_remove,
> +		.prepare_remove = acpi_memory_device_prepare_remove,
>   		},
>   };
> 
> @@ -448,6 +450,20 @@ static int acpi_memory_device_add(struct acpi_device *device)
>   static int acpi_memory_device_remove(struct acpi_device *device, int type)
>   {
>   	struct acpi_memory_device *mem_device = NULL;
> +
> +	if (!device || !acpi_driver_data(device))
> +		return -EINVAL;
> +
> +	mem_device = acpi_driver_data(device);
> +
> +	acpi_memory_device_free(mem_device);
> +
> +	return 0;
> +}
> +
> +static int acpi_memory_device_prepare_remove(struct acpi_device *device)
> +{
> +	struct acpi_memory_device *mem_device = NULL;
>   	int result;
> 
>   	if (!device || !acpi_driver_data(device))
> @@ -459,8 +475,6 @@ static int acpi_memory_device_remove(struct acpi_device *device, int type)
>   	if (result)
>   		return result;
> 
> -	acpi_memory_device_free(mem_device);
> -
>   	return 0;
>   }
> 
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