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

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Message-ID: <20120703183135.GE1727@t510.redhat.com>
Date:	Tue, 3 Jul 2012 15:31:36 -0300
From:	Rafael Aquini <aquini@...hat.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-mm@...ck.org, Rik van Riel <riel@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 1/4] mm: introduce compaction and migration for virtio
 ballooned pages

On Mon, Jul 02, 2012 at 08:36:02AM +0900, Minchan Kim wrote:
> 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!
> 
>
Nah, I'm the one who should be thanking everyone else here. :)

After a second thought I decided to follow your suggestion on this one as well.
Soon, I'll be posting the re-spin

Thanks Minchan!

Rafael
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