fsnotify: fsnotify_add_notify_event should return an event

Rather than the horrific void ** argument and such just to pass the
fanotify_merge event back to the caller of fsnotify_add_notify_event() have
those things return an event if it was different than the event suggusted to
be added.

Signed-off-by: Eric Paris <eparis@redhat.com>

5 files changed, 101 insertions, 95 deletions

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index bbcfccd4a8ea..f3c40c0e2b86 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -30,65 +30,58 @@ static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
         return false;
 }
 
-/* Note, if we return an event in *arg that a reference is being held... */
-static int fanotify_merge(struct list_head *list,
-                          struct fsnotify_event *event,
-                          void **arg)
+/* and the list better be locked by something too! */
+static struct fsnotify_event *fanotify_merge(struct list_head *list,
+                                             struct fsnotify_event *event)
 {
         struct fsnotify_event_holder *test_holder;
-        struct fsnotify_event *test_event;
+        struct fsnotify_event *test_event = NULL;
         struct fsnotify_event *new_event;
-        struct fsnotify_event **return_event = (struct fsnotify_event **)arg;
-        int ret = 0;
 
         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
 
-        *return_event = NULL;
-
-        /* and the list better be locked by something too! */
 
         list_for_each_entry_reverse(test_holder, list, event_list) {
-                test_event = test_holder->event;
-                if (should_merge(test_event, event)) {
-                        fsnotify_get_event(test_event);
-                        *return_event = test_event;
-
-                        ret = -EEXIST;
-                        /* if they are exactly the same we are done */
-                        if (test_event->mask == event->mask)
-                                goto out;
-
-                        /*
-                         * if the refcnt == 1 this is the only queue
-                         * for this event and so we can update the mask
-                         * in place.
-                         */
-                        if (atomic_read(&test_event->refcnt) == 1) {
-                                test_event->mask |= event->mask;
-                                goto out;
-                        }
-
-                        /* can't allocate memory, merge was no possible */
-                        new_event = fsnotify_clone_event(test_event);
-                        if (unlikely(!new_event)) {
-                                ret = 0;
-                                goto out;
-                        }
-
-                        /* we didn't return the test_event, so drop that ref */
-                        fsnotify_put_event(test_event);
-                        /* the reference we return on new_event is from clone */
-                        *return_event = new_event;
-
-                        /* build new event and replace it on the list */
-                        new_event->mask = (test_event->mask | event->mask);
-                        fsnotify_replace_event(test_holder, new_event);
-
+                if (should_merge(test_holder->event, event)) {
+                        test_event = test_holder->event;
                         break;
                 }
         }
-out:
-        return ret;
+
+        if (!test_event)
+                return NULL;
+
+        fsnotify_get_event(test_event);
+
+        /* if they are exactly the same we are done */
+        if (test_event->mask == event->mask)
+                return test_event;
+
+        /*
+         * if the refcnt == 2 this is the only queue
+         * for this event and so we can update the mask
+         * in place.
+         */
+        if (atomic_read(&test_event->refcnt) == 2) {
+                test_event->mask |= event->mask;
+                return test_event;
+        }
+
+        new_event = fsnotify_clone_event(test_event);
+
+        /* done with test_event */
+        fsnotify_put_event(test_event);
+
+        /* couldn't allocate memory, merge was not possible */
+        if (unlikely(!new_event))
+                return ERR_PTR(-ENOMEM);
+
+        /* build new event and replace it on the list */
+        new_event->mask = (test_event->mask | event->mask);
+        fsnotify_replace_event(test_holder, new_event);
+
+        /* we hold a reference on new_event from clone_event */
+        return new_event;
 }
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
@@ -123,7 +116,7 @@ static int fanotify_get_response_from_access(struct fsnotify_group *group,
 
 static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
 {
-        int ret;
+        int ret = 0;
         struct fsnotify_event *notify_event = NULL;
 
         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
@@ -138,13 +131,9 @@ static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_e
 
         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 
-        ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge,
-                                        (void **)&notify_event);
-        /* -EEXIST means this event was merged with another, not that it was an error */
-        if (ret == -EEXIST)
-                ret = 0;
-        if (ret)
-                goto out;
+        notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
+        if (IS_ERR(notify_event))
+                return PTR_ERR(notify_event);
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
         if (event->mask & FAN_ALL_PERM_EVENTS) {
@@ -155,9 +144,9 @@ static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_e
         }
 #endif
 
-out:
         if (notify_event)
                 fsnotify_put_event(notify_event);
+
         return ret;
 }
 
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index 906b72761b17..73a1106b3542 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -68,13 +68,11 @@ static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new
         return false;
 }
 
-static int inotify_merge(struct list_head *list,
-                         struct fsnotify_event *event,
-                         void **arg)
+static struct fsnotify_event *inotify_merge(struct list_head *list,
+                                            struct fsnotify_event *event)
 {
         struct fsnotify_event_holder *last_holder;
         struct fsnotify_event *last_event;
-        int ret = 0;
 
         /* and the list better be locked by something too */
         spin_lock(&event->lock);
@@ -82,11 +80,13 @@ static int inotify_merge(struct list_head *list,
         last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
         last_event = last_holder->event;
         if (event_compare(last_event, event))
-                ret = -EEXIST;
+                fsnotify_get_event(last_event);
+        else
+                last_event = NULL;
 
         spin_unlock(&event->lock);
 
-        return ret;
+        return last_event;
 }
 
 static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
@@ -96,7 +96,8 @@ static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_ev
         struct inode *to_tell;
         struct inotify_event_private_data *event_priv;
         struct fsnotify_event_private_data *fsn_event_priv;
-        int wd, ret;
+        struct fsnotify_event *added_event;
+        int wd, ret = 0;
 
         pr_debug("%s: group=%p event=%p to_tell=%p mask=%x\n", __func__, group,
                  event, event->to_tell, event->mask);
@@ -120,14 +121,13 @@ static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_ev
         fsn_event_priv->group = group;
         event_priv->wd = wd;
 
-        ret = fsnotify_add_notify_event(group, event, fsn_event_priv, inotify_merge, NULL);
-        if (ret) {
+        added_event = fsnotify_add_notify_event(group, event, fsn_event_priv, inotify_merge);
+        if (added_event) {
                 inotify_free_event_priv(fsn_event_priv);
-                /* EEXIST says we tail matched, EOVERFLOW isn't something
-                 * to report up the stack. */
-                if ((ret == -EEXIST) ||
-                    (ret == -EOVERFLOW))
-                        ret = 0;
+                if (!IS_ERR(added_event))
+                        fsnotify_put_event(added_event);
+                else
+                        ret = PTR_ERR(added_event);
         }
 
         if (fsn_mark->mask & IN_ONESHOT)
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 1068e1ca9cb0..a4cd227c4c76 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -516,7 +516,7 @@ void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,
                                     struct fsnotify_group *group)
 {
         struct inotify_inode_mark *i_mark;
-        struct fsnotify_event *ignored_event;
+        struct fsnotify_event *ignored_event, *notify_event;
         struct inotify_event_private_data *event_priv;
         struct fsnotify_event_private_data *fsn_event_priv;
         int ret;
@@ -538,9 +538,14 @@ void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,
         fsn_event_priv->group = group;
         event_priv->wd = i_mark->wd;
 
-        ret = fsnotify_add_notify_event(group, ignored_event, fsn_event_priv, NULL, NULL);
-        if (ret)
+        notify_event = fsnotify_add_notify_event(group, ignored_event, fsn_event_priv, NULL);
+        if (notify_event) {
+                if (IS_ERR(notify_event))
+                        ret = PTR_ERR(notify_event);
+                else
+                        fsnotify_put_event(notify_event);
                 inotify_free_event_priv(fsn_event_priv);
+        }
 
 skip_send_ignore:
 
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index e6dde25fb99b..f39260f8f865 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -137,16 +137,14 @@ struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnot
  * event off the queue to deal with.  If the event is successfully added to the
  * group's notification queue, a reference is taken on event.
  */
-int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
-                              struct fsnotify_event_private_data *priv,
-                              int (*merge)(struct list_head *,
-                                           struct fsnotify_event *,
-                                           void **arg),
-                              void **arg)
+struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
+                                                 struct fsnotify_event_private_data *priv,
+                                                 struct fsnotify_event *(*merge)(struct list_head *,
+                                                                                 struct fsnotify_event *))
 {
+        struct fsnotify_event *return_event = NULL;
         struct fsnotify_event_holder *holder = NULL;
         struct list_head *list = &group->notification_list;
-        int rc = 0;
 
         pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);
 
@@ -162,27 +160,37 @@ int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_even
 alloc_holder:
                 holder = fsnotify_alloc_event_holder();
                 if (!holder)
-                        return -ENOMEM;
+                        return ERR_PTR(-ENOMEM);
         }
 
         mutex_lock(&group->notification_mutex);
 
         if (group->q_len >= group->max_events) {
                 event = q_overflow_event;
-                rc = -EOVERFLOW;
+
+                /*
+                 * we need to return the overflow event
+                 * which means we need a ref
+                 */
+                fsnotify_get_event(event);
+                return_event = event;
+
                 /* sorry, no private data on the overflow event */
                 priv = NULL;
         }
 
         if (!list_empty(list) && merge) {
-                int ret;
+                struct fsnotify_event *tmp;
 
-                ret = merge(list, event, arg);
-                if (ret) {
+                tmp = merge(list, event);
+                if (tmp) {
                         mutex_unlock(&group->notification_mutex);
+
+                        if (return_event)
+                                fsnotify_put_event(return_event);
                         if (holder != &event->holder)
                                 fsnotify_destroy_event_holder(holder);
-                        return ret;
+                        return tmp;
                 }
         }
 
@@ -197,6 +205,12 @@ alloc_holder:
                  * event holder was used, go back and get a new one */
                 spin_unlock(&event->lock);
                 mutex_unlock(&group->notification_mutex);
+
+                if (return_event) {
+                        fsnotify_put_event(return_event);
+                        return_event = NULL;
+                }
+
                 goto alloc_holder;
         }
 
@@ -211,7 +225,7 @@ alloc_holder:
         mutex_unlock(&group->notification_mutex);
 
         wake_up(&group->notification_waitq);
-        return rc;
+        return return_event;
 }
 
 /*
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index a83859d7d36e..564b5ea4a831 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -379,13 +379,11 @@ extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struc
                                                                            struct fsnotify_event *event);
 
 /* attach the event to the group notification queue */
-extern int fsnotify_add_notify_event(struct fsnotify_group *group,
-                                     struct fsnotify_event *event,
-                                     struct fsnotify_event_private_data *priv,
-                                     int (*merge)(struct list_head *,
-                                                  struct fsnotify_event *,
-                                                  void **),
-                                     void **arg);
+extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
+                                                        struct fsnotify_event *event,
+                                                        struct fsnotify_event_private_data *priv,
+                                                        struct fsnotify_event *(*merge)(struct list_head *,
+                                                                                        struct fsnotify_event *));
 /* true if the group notification queue is empty */
 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 /* return, but do not dequeue the first event on the notification queue */