2 /* Watch queue and general notification mechanism, built on pipes
30 MODULE_DESCRIPTION("Watch queue");
91  * Post a notification to a watch queue.
183  * @wlist: The watch list to post the event to.
186  * @id: The ID to match on the watch.
188  * Post a notification of an event into a set of watch queues and let the users
201 	struct watch *watch;  in __post_watch_notification()  local
210 	hlist_for_each_entry_rcu(watch, &wlist->watchers, list_node) {  in __post_watch_notification()
211 		if (watch->id != id)  in __post_watch_notification()
214 		n->info |= watch->info_id;  in __post_watch_notification()
216 		wqueue = rcu_dereference(watch->queue);  in __post_watch_notification()
221 		if (security_post_notification(watch->cred, cred, n) < 0)  in __post_watch_notification()
314  * Set the filter on a watch queue.
415  * @wqueue: The watch queue to unref.
425 	struct watch *watch = container_of(rcu, struct watch, rcu);  in free_watch()  local
427 	put_watch_queue(rcu_access_pointer(watch->queue));  in free_watch()
428 	atomic_dec(&watch->cred->user->nr_watches);  in free_watch()
429 	put_cred(watch->cred);  in free_watch()
430 	kfree(watch);  in free_watch()
435 	struct watch *watch = container_of(kref, struct watch, usage);  in __put_watch()  local
437 	call_rcu(&watch->rcu, free_watch);  in __put_watch()
441  * Discard a watch.
443 static void put_watch(struct watch *watch)  in put_watch()  argument
445 	kref_put(&watch->usage, __put_watch);  in put_watch()
449  * init_watch - Initialise a watch
450  * @watch: The watch to initialise.
453  * Initialise a watch and set the watch queue.
455 void init_watch(struct watch *watch, struct watch_queue *wqueue)  in init_watch()  argument
457 	kref_init(&watch->usage);  in init_watch()
458 	INIT_HLIST_NODE(&watch->list_node);  in init_watch()
459 	INIT_HLIST_NODE(&watch->queue_node);  in init_watch()
460 	rcu_assign_pointer(watch->queue, wqueue);  in init_watch()
463 static int add_one_watch(struct watch *watch, struct watch_list *wlist, struct watch_queue *wqueue)  in add_one_watch()  argument
466 	struct watch *w;  in add_one_watch()
470 		if (wqueue == wq && watch->id == w->id)  in add_one_watch()
480 	watch->cred = get_cred(cred);  in add_one_watch()
481 	rcu_assign_pointer(watch->watch_list, wlist);  in add_one_watch()
484 	kref_get(&watch->usage);  in add_one_watch()
485 	hlist_add_head(&watch->queue_node, &wqueue->watches);  in add_one_watch()
486 	hlist_add_head_rcu(&watch->list_node, &wlist->watchers);  in add_one_watch()
491  * add_watch_to_object - Add a watch on an object to a watch list
492  * @watch: The watch to add
493  * @wlist: The watch list to add to
495  * @watch->queue must have been set to point to the queue to post notifications
496  * to and the watch list of the object to be watched.  @watch->cred must also
500  * locked against racing watch additions/removals.
502 int add_watch_to_object(struct watch *watch, struct watch_list *wlist)  in add_watch_to_object()  argument
509 	wqueue = rcu_access_pointer(watch->queue);  in add_watch_to_object()
512 		ret = add_one_watch(watch, wlist, wqueue);  in add_watch_to_object()
523  * remove_watch_from_object - Remove a watch or all watches from an object.
524  * @wlist: The watch list to remove from
525  * @wq: The watch queue of interest (ignored if @all is true)
526  * @id: The ID of the watch to remove (ignored if @all is true)
529  * Remove a specific watch or all watches from an object.  A notification is
537 	struct watch *watch;  in remove_watch_from_object()  local
544 	hlist_for_each_entry(watch, &wlist->watchers, list_node) {  in remove_watch_from_object()
546 		    (watch->id == id && rcu_access_pointer(watch->queue) == wq))  in remove_watch_from_object()
554 	hlist_del_init_rcu(&watch->list_node);  in remove_watch_from_object()
555 	rcu_assign_pointer(watch->watch_list, NULL);  in remove_watch_from_object()
558 	/* We now own the reference on watch that used to belong to wlist. */  in remove_watch_from_object()
560 	n.watch.type = WATCH_TYPE_META;  in remove_watch_from_object()
561 	n.watch.subtype = WATCH_META_REMOVAL_NOTIFICATION;  in remove_watch_from_object()
562 	n.watch.info = watch->info_id | watch_sizeof(n.watch);  in remove_watch_from_object()
565 		n.watch.info = watch->info_id | watch_sizeof(n);  in remove_watch_from_object()
567 	wqueue = rcu_dereference(watch->queue);  in remove_watch_from_object()
570 		post_one_notification(wqueue, &n.watch);  in remove_watch_from_object()
572 		if (!hlist_unhashed(&watch->queue_node)) {  in remove_watch_from_object()
573 			hlist_del_init_rcu(&watch->queue_node);  in remove_watch_from_object()
574 			put_watch(watch);  in remove_watch_from_object()
581 		void (*release_watch)(struct watch *);  in remove_watch_from_object()
585 		(*release_watch)(watch);  in remove_watch_from_object()
588 	put_watch(watch);  in remove_watch_from_object()
606 	struct watch *watch;  in watch_queue_clear()  local
619 		watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);  in watch_queue_clear()
620 		hlist_del_init_rcu(&watch->queue_node);  in watch_queue_clear()
621 		/* We now own a ref on the watch. */  in watch_queue_clear()
629 		wlist = rcu_dereference(watch->watch_list);  in watch_queue_clear()
631 			void (*release_watch)(struct watch *);  in watch_queue_clear()
635 			release = !hlist_unhashed(&watch->list_node);  in watch_queue_clear()
637 				hlist_del_init_rcu(&watch->list_node);  in watch_queue_clear()
638 				rcu_assign_pointer(watch->watch_list, NULL);  in watch_queue_clear()
640 				/* We now own a second ref on the watch. */  in watch_queue_clear()
652 					(*release_watch)(watch);  in watch_queue_clear()
655 				put_watch(watch);  in watch_queue_clear()
659 		put_watch(watch);  in watch_queue_clear()
668  * get_watch_queue - Get a watch queue from its file descriptor.
690  * Initialise a watch queue