linux-kernel - Re: [RFC 08/15] PM / Hibernate: add user module

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Message-Id: <201003252307.15232.rjw@sisk.pl>
Date:	Thu, 25 Mar 2010 23:07:15 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	jirislaby@...il.com, pavel@....cz,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Nigel Cunningham <ncunningham@...a.org.au>
Subject: Re: [RFC 08/15] PM / Hibernate: add user module_ops

On Tuesday 23 March 2010, Jiri Slaby wrote:
> Add sws_module_ops into /dev/snapshot user interface, so far only with
> .storage_available. The structure will be shortly filled while converting
> it to ops.
> 
> Also, when using this interface, switch to the ops on open/release.

Quite frankly, I don't really understand the purpose of this change in this
particular form.  It looks like it may be folded into one of the subsequent
changes just fine.

Rafael


> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Nigel Cunningham <ncunningham@...a.org.au>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> ---
>  kernel/power/user.c |   15 +++++++++++++++
>  1 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 68a99c1..20bf34c 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -61,10 +61,20 @@ static struct snapshot_data {
>  	char frozen;
>  	char ready;
>  	char platform_support;
> +	struct sws_module_ops *prev_ops;
>  } snapshot_state;
>  
>  atomic_t snapshot_device_available = ATOMIC_INIT(1);
>  
> +static unsigned long user_storage_available(void)
> +{
> +	return ~0UL; /* we have no idea, maybe we will fail later */
> +}
> +
> +struct sws_module_ops user_ops = {
> +	.storage_available = user_storage_available,
> +};
> +
>  static int snapshot_open(struct inode *inode, struct file *filp)
>  {
>  	struct snapshot_data *data;
> @@ -115,6 +125,10 @@ static int snapshot_open(struct inode *inode, struct file *filp)
>  	}
>  	if (error)
>  		atomic_inc(&snapshot_device_available);
> +	else {
> +		data->prev_ops = sws_io_ops;
> +		sws_io_ops = &user_ops;
> +	}
>  	data->frozen = 0;
>  	data->ready = 0;
>  	data->platform_support = 0;
> @@ -139,6 +153,7 @@ static int snapshot_release(struct inode *inode, struct file *filp)
>  		thaw_processes();
>  	pm_notifier_call_chain(data->mode == O_WRONLY ?
>  			PM_POST_HIBERNATION : PM_POST_RESTORE);
> +	sws_io_ops = data->prev_ops;
>  	atomic_inc(&snapshot_device_available);
>  
>  	mutex_unlock(&pm_mutex);
> 

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