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fsnotify: generic notification queue and waitq

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inotify needs to do asyc notification in which event information is stored
on a queue until the listener is ready to receive it.  This patch
implements a generic notification queue for inotify (and later fanotify) to
store events to be sent at a later time.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Eric Paris 2009-05-21 17:01:37 -04:00
parent 3c5119c05d
commit a2d8bc6cb4
4 changed files with 281 additions and 10 deletions
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37
include/linux/fsnotify_backend.h
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@ -119,6 +119,13 @@ struct fsnotify_group {
const struct fsnotify_ops *ops; /* how this group handles things */
/* needed to send notification to userspace */
struct mutex notification_mutex; /* protect the notification_list */
struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
unsigned int q_len; /* events on the queue */
unsigned int max_events; /* maximum events allowed on the list */
/* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
spinlock_t mark_lock; /* protect mark_entries list */
atomic_t num_marks; /* 1 for each mark entry and 1 for not being
@ -135,12 +142,33 @@ struct fsnotify_group {
};
};
/*
* A single event can be queued in multiple group->notification_lists.
*
* each group->notification_list will point to an event_holder which in turns points
* to the actual event that needs to be sent to userspace.
*
* Seemed cheaper to create a refcnt'd event and a small holder for every group
* than create a different event for every group
*
*/
struct fsnotify_event_holder {
struct fsnotify_event *event;
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.
*/
struct fsnotify_event {
/*
* If we create an event we are also likely going to need a holder
* to link to a group. So embed one holder in the event. Means only
* one allocation for the common case where we only have one group
*/
struct fsnotify_event_holder holder;
spinlock_t lock; /* protection for the associated event_holder and private_list */
/* to_tell may ONLY be dereferenced during handle_event(). */
struct inode *to_tell; /* either the inode the event happened to or its parent */
@ -264,6 +292,15 @@ extern void fsnotify_put_event(struct fsnotify_event *event);
extern struct fsnotify_event_private_data *fsnotify_get_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);
/* 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);
/* functions used to manipulate the marks attached to inodes */
/* run all marks associated with an inode and update inode->i_fsnotify_mask */