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SubjectRe: [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks
Hi Rafael,

Please see below.

On 05/04/2013 07:21 PM, Rafael J. Wysocki wrote:
......
> static BLOCKING_NOTIFIER_HEAD(memory_chain);
> @@ -278,33 +283,64 @@ static int __memory_block_change_state(s
> {
> int ret = 0;
>
> - if (mem->state != from_state_req) {
> - ret = -EINVAL;
> - goto out;
> - }
> + if (mem->state != from_state_req)
> + return -EINVAL;
>
> if (to_state == MEM_OFFLINE)
> mem->state = MEM_GOING_OFFLINE;
>
> ret = memory_block_action(mem->start_section_nr, to_state, online_type);
> -
> if (ret) {
> mem->state = from_state_req;
> - goto out;
> + } else {
> + mem->state = to_state;
> + if (to_state == MEM_ONLINE)
> + mem->last_online = online_type;

Why do we need to remember last online type ?

And as far as I know, we can obtain which zone a page was in last time it
was onlined by check page->flags, just like online_pages() does. If we
use online_kernel or online_movable, the zone boundary will be
recalculated.
So we don't need to remember the last online type.

Seeing from your patch, I guess memory_subsys_online() can only handle
online and offline. So mem->last_online is used to remember what user has
done through the original way to trigger memory hot-remove, right ? And
when
user does it in this new way, it just does the same thing as user does last
time.

But I still think we don't need to remember it because if finally you call
online_pages(), it just does the same thing as last time by default.

online_pages()
{
......
if (online_type == ONLINE_KERNEL ......

if (online_type == ONLINE_MOVABLE......

zone = page_zone(pfn_to_page(pfn));

/* Here, the page will be put into the zone which it belong to last
time. */

......
}

I just thought of it. Maybe I missed something in your design. Please tell
me if I'm wrong.

Reviewed-by: Tang Chen <tangchen@cn.fujitsu.com>

Thanks. :)




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