Re: [PATCH v2 1/4] mm: introduce compaction and migration for virtio ballooned pages

[Minchan Kim <minchan@kernel.org>]

On 06/30/2012 10:34 AM, Rafael Aquini wrote:

>> void isolate_page_from_balloonlist(struct page* page)
>> > {
>> > 	page->mapping->a_ops->invalidatepage(page, 0);
>> > }
>> > 
>> > 	if (is_balloon_page(page) && (page_count(page) == 2)) {
>> > 		isolate_page_from_balloonlist(page);
>> > 	}
>> > 
> Humm, my feelings on your approach here: just an unecessary indirection that
> doesn't bring the desired code readability improvement.
> If the header comment statement on balloon_mapping->a_ops is not clear enough 
> on those methods usage for ballooned pages:
> 
> ..... 
> /*
>  * Balloon pages special page->mapping.
>  * users must properly allocate and initialize an instance of balloon_mapping,
>  * and set it as the page->mapping for balloon enlisted page instances.
>  *
>  * address_space_operations necessary methods for ballooned pages:
>  *   .migratepage    - used to perform balloon's page migration (as is)
>  *   .invalidatepage - used to isolate a page from balloon's page list
>  *   .freepage       - used to reinsert an isolated page to balloon's page list
>  */
> struct address_space *balloon_mapping;
> EXPORT_SYMBOL_GPL(balloon_mapping);
> .....
> 
> I can add an extra commentary, to recollect folks about that usage, next to the
> points where those callbacks are used at isolate_balloon_page() &
> putback_balloon_page(). What do you think?
> 
> 


I am not strongly against you.
It trivial nitpick must not prevent your great work. :)

Thanks!


-- 
Kind regards,
Minchan Kim

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