1 files changed, 36 insertions, 22 deletions

diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 2c351765c409..59ddb00d6944 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -454,6 +454,33 @@ void init_watch(struct watch *watch, struct watch_queue *wqueue)
 	rcu_assign_pointer(watch->queue, wqueue);
 }
 
+static int add_one_watch(struct watch *watch, struct watch_list *wlist, struct watch_queue *wqueue)
+{
+	const struct cred *cred;
+	struct watch *w;
+
+	hlist_for_each_entry(w, &wlist->watchers, list_node) {
+		struct watch_queue *wq = rcu_access_pointer(w->queue);
+		if (wqueue == wq && watch->id == w->id)
+			return -EBUSY;
+	}
+
+	cred = current_cred();
+	if (atomic_inc_return(&cred->user->nr_watches) > task_rlimit(current, RLIMIT_NOFILE)) {
+		atomic_dec(&cred->user->nr_watches);
+		return -EAGAIN;
+	}
+
+	watch->cred = get_cred(cred);
+	rcu_assign_pointer(watch->watch_list, wlist);
+
+	kref_get(&wqueue->usage);
+	kref_get(&watch->usage);
+	hlist_add_head(&watch->queue_node, &wqueue->watches);
+	hlist_add_head_rcu(&watch->list_node, &wlist->watchers);
+	return 0;
+}
+
 /**
  * add_watch_to_object - Add a watch on an object to a watch list
  * @watch: The watch to add
@@ -468,34 +495,21 @@ void init_watch(struct watch *watch, struct watch_queue *wqueue)
  */
 int add_watch_to_object(struct watch *watch, struct watch_list *wlist)
 {
-	struct watch_queue *wqueue = rcu_access_pointer(watch->queue);
-	struct watch *w;
-
-	hlist_for_each_entry(w, &wlist->watchers, list_node) {
-		struct watch_queue *wq = rcu_access_pointer(w->queue);
-		if (wqueue == wq && watch->id == w->id)
-			return -EBUSY;
-	}
-
-	watch->cred = get_current_cred();
-	rcu_assign_pointer(watch->watch_list, wlist);
+	struct watch_queue *wqueue;
+	int ret = -ENOENT;
 
-	if (atomic_inc_return(&watch->cred->user->nr_watches) >
-	    task_rlimit(current, RLIMIT_NOFILE)) {
-		atomic_dec(&watch->cred->user->nr_watches);
-		put_cred(watch->cred);
-		return -EAGAIN;
-	}
+	rcu_read_lock();
 
+	wqueue = rcu_access_pointer(watch->queue);
 	if (lock_wqueue(wqueue)) {
-		kref_get(&wqueue->usage);
-		kref_get(&watch->usage);
-		hlist_add_head(&watch->queue_node, &wqueue->watches);
+		spin_lock(&wlist->lock);
+		ret = add_one_watch(watch, wlist, wqueue);
+		spin_unlock(&wlist->lock);
 		unlock_wqueue(wqueue);
 	}
 
-	hlist_add_head_rcu(&watch->list_node, &wlist->watchers);
-	return 0;
+	rcu_read_unlock();
+	return ret;
 }
 EXPORT_SYMBOL(add_watch_to_object);