fsnotify: allow groups to add private data to events

inotify needs per group information attached to events.  This patch allows
groups to attach private information and implements a callback so that
information can be freed when an event is being destroyed.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>

1 files changed, 19 insertions, 5 deletions

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index b78b5573d227..efdf9e442d86 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -63,6 +63,7 @@
 struct fsnotify_group;
 struct fsnotify_event;
 struct fsnotify_mark_entry;
+struct fsnotify_event_private_data;
 
 /*
  * Each group much define these ops.  The fsnotify infrastructure will call
@@ -81,6 +82,7 @@ struct fsnotify_ops {
         int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
         void (*free_group_priv)(struct fsnotify_group *group);
         void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
+        void (*free_event_priv)(struct fsnotify_event_private_data *priv);
 };
 
 /*
@@ -158,6 +160,15 @@ struct fsnotify_event_holder {
 };
 
 /*
+ * Inotify needs to tack data onto an event.  This struct lets us later find the
+ * correct private data of the correct group.
+ */
+struct fsnotify_event_private_data {
+        struct fsnotify_group *group;
+        struct list_head event_list;
+};
+
+/*
  * all of the information about the original object we want to now send to
  * a group.  If you want to carry more info from the accessing task to the
  * listener this structure is where you need to be adding fields.
@@ -196,6 +207,8 @@ struct fsnotify_event {
         u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
         char *file_name;
         size_t name_len;
+
+        struct list_head private_data_list;     /* groups can store private data here */
 };
 
 /*
@@ -294,17 +307,18 @@ extern void fsnotify_put_group(struct fsnotify_group *group);
 /* take a reference to an event */
 extern void fsnotify_get_event(struct fsnotify_event *event);
 extern void fsnotify_put_event(struct fsnotify_event *event);
-/* find private data previously attached to an event */
-extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
-                                                                        struct fsnotify_event *event);
+/* find private data previously attached to an event and unlink it */
+extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
+                                                                           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);
+extern int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
+                                     struct fsnotify_event_private_data *priv);
 /* 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 */
 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
-/* reutnr AND dequeue the first event on the notification queue */
+/* return AND dequeue the first event on the notification queue */
 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 
 /* functions used to manipulate the marks attached to inodes */