linux-kernel - Re: [PATCH 4/5] ACPI / scan: Add second pass of companion offlining to hot-remove code

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Date:	Tue, 21 May 2013 15:34:37 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Toshi Kani <toshi.kani@...com>,
	Wen Congyang <wency@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiang Liu <liuj97@...il.com>,
	Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>,
	<linux-mm@...ck.org>
Subject: Re: [PATCH 4/5] ACPI / scan: Add second pass of companion offlining
 to hot-remove code

On 2013/5/19 7:34, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> As indicated by comments in mm/memory_hotplug.c:remove_memory(),
> if CONFIG_MEMCG is set, it may not be possible to offline all of the
> memory blocks held by one module (FRU) in one pass (because one of
> them may be used by the others to store page cgroup in that case
> and that block has to be offlined before the other ones).
> 
> To handle that arguably corner case, add a second pass of companion
> device offlining to acpi_scan_hot_remove() and make it ignore errors
> returned in the first pass (and make it skip the second pass if the
> first one is successful).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/scan.c |   67 ++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 50 insertions(+), 17 deletions(-)
> 
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -131,6 +131,7 @@ static acpi_status acpi_bus_offline_comp
>  {
>  	struct acpi_device *device = NULL;
>  	struct acpi_device_physical_node *pn;
> +	bool second_pass = (bool)data;
>  	acpi_status status = AE_OK;
>  
>  	if (acpi_bus_get_device(handle, &device))
> @@ -141,15 +142,26 @@ static acpi_status acpi_bus_offline_comp
>  	list_for_each_entry(pn, &device->physical_node_list, node) {
>  		int ret;
>  
> +		if (second_pass) {
> +			/* Skip devices offlined by the first pass. */
> +			if (pn->put_online)

should it be "if (!pn->put_online)" ?

Thanks
Xishi Qiu

> +				continue;
> +		} else {
> +			pn->put_online = false;
> +		}
>  		ret = device_offline(pn->dev);
>  		if (acpi_force_hot_remove)
>  			continue;
>  
> -		if (ret < 0) {
> -			status = AE_ERROR;
> -			break;
> +		if (ret >= 0) {
> +			pn->put_online = !ret;
> +		} else {
> +			*ret_p = pn->dev;
> +			if (second_pass) {
> +				status = AE_ERROR;
> +				break;
> +			}
>  		}
> -		pn->put_online = !ret;
>  	}
>  
>  	mutex_unlock(&device->physical_node_lock);



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