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>

1 files changed, 46 insertions, 57 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;
 }