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Date: Tue, 21 Aug 2012 14:55:03 -0300 From: Rafael Aquini <aquini@...hat.com> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, Rusty Russell <rusty@...tcorp.com.au>, Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>, Andi Kleen <andi@...stfloor.org>, Andrew Morton <akpm@...ux-foundation.org>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Minchan Kim <minchan@...nel.org> Subject: Re: [PATCH v8 1/5] mm: introduce a common interface for balloon pages mobility On Tue, Aug 21, 2012 at 04:52:23PM +0300, Michael S. Tsirkin wrote: > > + * address_space_operations utilized methods for ballooned pages: > > + * .migratepage - used to perform balloon's page migration (as is) > > + * .launder_page - used to isolate a page from balloon's page list > > + * .freepage - used to reinsert an isolated page to balloon's page list > > + */ > > It would be a good idea to document the assumptions here. > Looks like .launder_page and .freepage are called in rcu critical > section. > But migratepage isn't - why is that safe? > The migratepage callback for virtio_balloon can sleep, and IIUC we cannot sleep within a RCU critical section. Also, The migratepage callback is called at inner migration's circle function move_to_new_page(), and I don't think embedding it in a RCU critical section would be a good idea, for the same understanding aforementioned. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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