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Subject[PATCH 09/12] fsnotify: allow groups to add private data to events
Date
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>
---
fs/notify/dnotify/dnotify.c | 1 +
fs/notify/notification.c | 37 ++++++++++++++++++++++++++++++++++---
include/linux/fsnotify_backend.h | 17 ++++++++++++++++-
3 files changed, 51 insertions(+), 4 deletions(-)
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index d9d80f5..12f9e6b 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -183,6 +183,7 @@ static struct fsnotify_ops dnotify_fsnotify_ops = {
.should_send_event = dnotify_should_send_event,
.free_group_priv = NULL,
.freeing_mark = dnotify_freeing_mark,
+ .free_event_priv = NULL,
};

/*
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 346f6e5..3e6e364 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -90,6 +90,8 @@ void fsnotify_put_event(struct fsnotify_event *event)
if (event->data_type == FSNOTIFY_EVENT_PATH)
path_put(&event->path);

+ BUG_ON(!list_empty(&event->private_data_list));
+
kfree(event->file_name);
kmem_cache_free(fsnotify_event_cachep, event);
}
@@ -106,7 +108,26 @@ void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
}

/*
- * check if 2 events contain the same information.
+ * Find the private data that the group previously attached to this event when
+ * the group added the event to the notification queue (fsnotify_add_notify_event)
+ */
+struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event)
+{
+ struct fsnotify_event_private_data *lpriv;
+ struct fsnotify_event_private_data *priv = NULL;
+
+ list_for_each_entry(lpriv, &event->private_data_list, event_list) {
+ if (lpriv->group == group) {
+ priv = lpriv;
+ break;
+ }
+ }
+ return priv;
+}
+
+/*
+ * Check if 2 events contain the same information. We do not compare private data
+ * but at this moment that isn't a problem for any know fsnotify listeners.
*/
static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
{
@@ -134,13 +155,17 @@ static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new
* 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)
+int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
+ struct fsnotify_event_private_data *priv)
{
struct fsnotify_event_holder *holder = NULL;
struct list_head *list = &group->notification_list;
struct fsnotify_event_holder *last_holder;
struct fsnotify_event *last_event;

+ /* easy to tell if priv was attached to the event */
+ INIT_LIST_HEAD(&priv->event_list);
+
/*
* There is one fsnotify_event_holder embedded inside each fsnotify_event.
* Check if we expect to be able to use that holder. If not alloc a new
@@ -183,7 +208,7 @@ alloc_holder:
mutex_unlock(&group->notification_mutex);
if (holder != &event->holder)
fsnotify_destroy_event_holder(holder);
- return 0;
+ return -EEXIST;
}
}

@@ -192,6 +217,8 @@ alloc_holder:

fsnotify_get_event(event);
list_add_tail(&holder->event_list, list);
+ if (priv)
+ list_add_tail(&priv->event_list, &event->private_data_list);
spin_unlock(&event->lock);
mutex_unlock(&group->notification_mutex);

@@ -256,6 +283,8 @@ void fsnotify_flush_notify(struct fsnotify_group *group)
mutex_lock(&group->notification_mutex);
while (!fsnotify_notify_queue_is_empty(group)) {
event = fsnotify_remove_notify_event(group);
+ if (group->ops->free_event_priv)
+ group->ops->free_event_priv(group, event);
fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
}
mutex_unlock(&group->notification_mutex);
@@ -274,6 +303,8 @@ static void initialize_event(struct fsnotify_event *event)
event->inode = NULL;
event->data_type = FSNOTIFY_EVENT_NONE;

+ INIT_LIST_HEAD(&event->private_data_list);
+
event->to_tell = NULL;

event->file_name = NULL;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index b78b557..de5c793 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -81,6 +81,7 @@ 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_group *group, struct fsnotify_event *event);
};

/*
@@ -158,6 +159,15 @@ 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 +206,8 @@ 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 */
};

/*
@@ -299,13 +311,16 @@ extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct f
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 */
extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
+extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
+ struct fsnotify_event *event);

/* functions used to manipulate the marks attached to inodes */



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