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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>