2 /* Watch queue and general notification mechanism, built on pipes
30 MODULE_DESCRIPTION("Watch queue");
91  * Post a notification to a watch queue.
182  * @wlist: The watch list to post the event to.
185  * @id: The ID to match on the watch.
187  * Post a notification of an event into a set of watch queues and let the users
200 	struct watch *watch;  in __post_watch_notification()  local
209 	hlist_for_each_entry_rcu(watch, &wlist->watchers, list_node) {  in __post_watch_notification()
210 		if (watch->id != id)  in __post_watch_notification()
213 		n->info |= watch->info_id;  in __post_watch_notification()
215 		wqueue = rcu_dereference(watch->queue);  in __post_watch_notification()
220 		if (security_post_notification(watch->cred, cred, n) < 0)  in __post_watch_notification()
313  * Set the filter on a watch queue.
414  * @wqueue: The watch queue to unref.
424 	struct watch *watch = container_of(rcu, struct watch, rcu);  in free_watch()  local
426 	put_watch_queue(rcu_access_pointer(watch->queue));  in free_watch()
427 	atomic_dec(&watch->cred->user->nr_watches);  in free_watch()
428 	put_cred(watch->cred);  in free_watch()
429 	kfree(watch);  in free_watch()
434 	struct watch *watch = container_of(kref, struct watch, usage);  in __put_watch()  local
436 	call_rcu(&watch->rcu, free_watch);  in __put_watch()
440  * Discard a watch.
442 static void put_watch(struct watch *watch)  in put_watch()  argument
444 	kref_put(&watch->usage, __put_watch);  in put_watch()
448  * init_watch - Initialise a watch
449  * @watch: The watch to initialise.
452  * Initialise a watch and set the watch queue.
454 void init_watch(struct watch *watch, struct watch_queue *wqueue)  in init_watch()  argument
456 	kref_init(&watch->usage);  in init_watch()
457 	INIT_HLIST_NODE(&watch->list_node);  in init_watch()
458 	INIT_HLIST_NODE(&watch->queue_node);  in init_watch()
459 	rcu_assign_pointer(watch->queue, wqueue);  in init_watch()
462 static int add_one_watch(struct watch *watch, struct watch_list *wlist, struct watch_queue *wqueue)  in add_one_watch()  argument
465 	struct watch *w;  in add_one_watch()
469 		if (wqueue == wq && watch->id == w->id)  in add_one_watch()
479 	watch->cred = get_cred(cred);  in add_one_watch()
480 	rcu_assign_pointer(watch->watch_list, wlist);  in add_one_watch()
483 	kref_get(&watch->usage);  in add_one_watch()
484 	hlist_add_head(&watch->queue_node, &wqueue->watches);  in add_one_watch()
485 	hlist_add_head_rcu(&watch->list_node, &wlist->watchers);  in add_one_watch()
490  * add_watch_to_object - Add a watch on an object to a watch list
491  * @watch: The watch to add
492  * @wlist: The watch list to add to
494  * @watch->queue must have been set to point to the queue to post notifications
495  * to and the watch list of the object to be watched.  @watch->cred must also
499  * locked against racing watch additions/removals.
501 int add_watch_to_object(struct watch *watch, struct watch_list *wlist)  in add_watch_to_object()  argument
508 	wqueue = rcu_access_pointer(watch->queue);  in add_watch_to_object()
511 		ret = add_one_watch(watch, wlist, wqueue);  in add_watch_to_object()
522  * remove_watch_from_object - Remove a watch or all watches from an object.
523  * @wlist: The watch list to remove from
524  * @wq: The watch queue of interest (ignored if @all is true)
525  * @id: The ID of the watch to remove (ignored if @all is true)
528  * Remove a specific watch or all watches from an object.  A notification is
536 	struct watch *watch;  in remove_watch_from_object()  local
543 	hlist_for_each_entry(watch, &wlist->watchers, list_node) {  in remove_watch_from_object()
545 		    (watch->id == id && rcu_access_pointer(watch->queue) == wq))  in remove_watch_from_object()
553 	hlist_del_init_rcu(&watch->list_node);  in remove_watch_from_object()
554 	rcu_assign_pointer(watch->watch_list, NULL);  in remove_watch_from_object()
557 	/* We now own the reference on watch that used to belong to wlist. */  in remove_watch_from_object()
559 	n.watch.type = WATCH_TYPE_META;  in remove_watch_from_object()
560 	n.watch.subtype = WATCH_META_REMOVAL_NOTIFICATION;  in remove_watch_from_object()
561 	n.watch.info = watch->info_id | watch_sizeof(n.watch);  in remove_watch_from_object()
564 		n.watch.info = watch->info_id | watch_sizeof(n);  in remove_watch_from_object()
566 	wqueue = rcu_dereference(watch->queue);  in remove_watch_from_object()
569 		post_one_notification(wqueue, &n.watch);  in remove_watch_from_object()
571 		if (!hlist_unhashed(&watch->queue_node)) {  in remove_watch_from_object()
572 			hlist_del_init_rcu(&watch->queue_node);  in remove_watch_from_object()
573 			put_watch(watch);  in remove_watch_from_object()
580 		void (*release_watch)(struct watch *);  in remove_watch_from_object()
584 		(*release_watch)(watch);  in remove_watch_from_object()
587 	put_watch(watch);  in remove_watch_from_object()
605 	struct watch *watch;  in watch_queue_clear()  local
618 		watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);  in watch_queue_clear()
619 		hlist_del_init_rcu(&watch->queue_node);  in watch_queue_clear()
620 		/* We now own a ref on the watch. */  in watch_queue_clear()
628 		wlist = rcu_dereference(watch->watch_list);  in watch_queue_clear()
630 			void (*release_watch)(struct watch *);  in watch_queue_clear()
634 			release = !hlist_unhashed(&watch->list_node);  in watch_queue_clear()
636 				hlist_del_init_rcu(&watch->list_node);  in watch_queue_clear()
637 				rcu_assign_pointer(watch->watch_list, NULL);  in watch_queue_clear()
639 				/* We now own a second ref on the watch. */  in watch_queue_clear()
651 					(*release_watch)(watch);  in watch_queue_clear()
654 				put_watch(watch);  in watch_queue_clear()
658 		put_watch(watch);  in watch_queue_clear()
667  * get_watch_queue - Get a watch queue from its file descriptor.
689  * Initialise a watch queue