Re: [PATCH] uswsusp: automatically free the in-memory image once s2disk has finished with it

Pavel Machek
2009-12-02T21:11:10Z

On Wed 2009-12-02 14:28:12, Alan Jenkins wrote:
> The original in-kernel suspend (swsusp) frees the in-memory hibernation
> image before powering off the machine. s2disk doesn't, so there is
> _much_ less free memory when it tries to power off.
>
> This is a gratuitous difference. The userspace suspend interface
> /dev/snapshot only allows the hibernation image to be read once.
> Once the s2disk program has read the last page, we can free the entire
> image.
>
> This avoids a hang after writing the hibernation image which was
> triggered by commit 5f8dcc21211a3d4e3a7a5ca366b469fb88117f61
> "page-allocator: split per-cpu list into one-list-per-migrate-type":

Yes, you work around page-allocator hang. But is it right thing to do?

I mean... Power down should not be too memory-critical. Why can't new
page allocator handle that?

(And yes, when page allocator is fixed we may want to do something
like that, but...)

Pavel

> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -165,6 +165,10 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
> res = -EFAULT;
> else
> *offp = data->handle.offset;
> + } else {
> + swsusp_free();
> + memset(&data->handle, 0, sizeof(struct snapshot_handle));
> + data->ready = 0;
> }
>
> Unlock:

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