fsnotify: clone existing events

fsnotify_clone_event will take an event, clone it, and return the cloned
event to the caller.  Since events may be in use by multiple fsnotify
groups simultaneously certain event entries (such as the mask) cannot be
changed after the event was created.  Since fanotify would like to merge
events happening on the same file it needs a new clean event to work with
so it can change any fields it wishes.

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

1 files changed, 25 insertions, 4 deletions

diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 6dc96b3..bc9470c 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -284,11 +284,33 @@ static void initialize_event(struct fsnotify_event *event)
 
 	spin_lock_init(&event->lock);
 
-	event->data_type = FSNOTIFY_EVENT_NONE;
-
 	INIT_LIST_HEAD(&event->private_data_list);
 }
 
+struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event)
+{
+	struct fsnotify_event *event;
+
+	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
+	if (!event)
+		return NULL;
+
+	memcpy(event, old_event, sizeof(*event));
+	initialize_event(event);
+
+	if (event->name_len) {
+		event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
+		if (!event->file_name) {
+			kmem_cache_free(fsnotify_event_cachep, event);
+			return NULL;
+		}
+	}
+	if (event->data_type == FSNOTIFY_EVENT_PATH)
+		path_get(&event->path);
+
+	return event;
+}
+
 /*
  * fsnotify_create_event - Allocate a new event which will be sent to each
  * group's handle_event function if the group was interested in this
@@ -324,6 +346,7 @@ struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 
 	event->sync_cookie = cookie;
 	event->to_tell = to_tell;
+	event->data_type = data_type;
 
 	switch (data_type) {
 	case FSNOTIFY_EVENT_FILE: {
@@ -340,12 +363,10 @@ struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 		event->path.dentry = path->dentry;
 		event->path.mnt = path->mnt;
 		path_get(&event->path);
-		event->data_type = FSNOTIFY_EVENT_PATH;
 		break;
 	}
 	case FSNOTIFY_EVENT_INODE:
 		event->inode = data;
-		event->data_type = FSNOTIFY_EVENT_INODE;
 		break;
 	case FSNOTIFY_EVENT_NONE:
 		event->inode = NULL;