Re: [RFC 09/15] PM / Hibernate: user, implement user_ops writer

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Switch /dev/snapshot writer to sws_module_ops approach so that we
> can transparently rewrite the rest of the snapshot from pages pulling
> to their pushing through layers.
> 
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> Cc: Nigel Cunningham <ncunningham@crca.org.au>
> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
> ---
>  kernel/power/user.c |  113 +++++++++++++++++++++++++++++++++++++++++++++++----
>  1 files changed, 105 insertions(+), 8 deletions(-)
>

> +	if (test_bit(TODO_CLOSED, to_do_flags))
> +		return -EIO;
> +
> +	to_do_buf = buf;
> +	wmb();
> +	set_bit(TODO_WORK, to_do_flags);
> +	wake_up_interruptible(&to_do_wait);

Uhuh, open-coded barriers... these need to be commented, and I guess
you just should not play this kind of trickery.

spnlocks? Normal locks?

> +
> +	wait_event(to_do_done, !test_bit(TODO_WORK, to_do_flags) ||
> +			(err = test_bit(TODO_CLOSED, to_do_flags)));
> +
> +	return err ? -EIO : 0;
> +}
> +
> +static int put_user_writer(unsigned int flags, int error)
> +{
> +	int err = 0;
> +
> +	if (error)
> +		set_bit(TODO_ERROR, to_do_flags);
> +	set_bit(TODO_FINISH, to_do_flags);
> +	wake_up_interruptible(&to_do_wait);
> +
> +	wait_event(to_do_done, !test_bit(TODO_FINISH, to_do_flags) ||
> +			(err = test_bit(TODO_CLOSED, to_do_flags)));
> +
> +	if (!error && err)
> +		error = -EIO;
> +
> +	return error;
> +}
> +
>  struct sws_module_ops user_ops = {
									Pavel

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