fsnotify: generic notification queue and waitq
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>wifi-calibration
Eric Paris
parent
3c5119c05d
commit
a2d8bc6cb4
|
|
@ -13,8 +13,12 @@ extern struct list_head fsnotify_groups;
|
|||
/* all bitwise OR of all event types (FS_*) for all fsnotify_groups */
|
||||
extern __u32 fsnotify_mask;
|
||||
|
||||
/* destroy all events sitting in this groups notification queue */
|
||||
extern void fsnotify_flush_notify(struct fsnotify_group *group);
|
||||
|
||||
/* final kfree of a group */
|
||||
extern void fsnotify_final_destroy_group(struct fsnotify_group *group);
|
||||
|
||||
/* run the list of all marks associated with inode and flag them to be freed */
|
||||
extern void fsnotify_clear_marks_by_inode(struct inode *inode);
|
||||
/*
|
||||
|
|
@ -22,4 +26,9 @@ extern void fsnotify_clear_marks_by_inode(struct inode *inode);
|
|||
* about events that happen to its children.
|
||||
*/
|
||||
extern void __fsnotify_update_child_dentry_flags(struct inode *inode);
|
||||
|
||||
/* allocate and destroy and event holder to attach events to notification/access queues */
|
||||
extern struct fsnotify_event_holder *fsnotify_alloc_event_holder(void);
|
||||
extern void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder);
|
||||
|
||||
#endif /* __FS_NOTIFY_FSNOTIFY_H_ */
|
||||
|
|
|
|||
|
|
@ -91,6 +91,9 @@ static void fsnotify_get_group(struct fsnotify_group *group)
|
|||
*/
|
||||
void fsnotify_final_destroy_group(struct fsnotify_group *group)
|
||||
{
|
||||
/* clear the notification queue of all events */
|
||||
fsnotify_flush_notify(group);
|
||||
|
||||
if (group->ops->free_group_priv)
|
||||
group->ops->free_group_priv(group);
|
||||
|
||||
|
|
@ -214,6 +217,12 @@ struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
|
|||
group->group_num = group_num;
|
||||
group->mask = mask;
|
||||
|
||||
mutex_init(&group->notification_mutex);
|
||||
INIT_LIST_HEAD(&group->notification_list);
|
||||
init_waitqueue_head(&group->notification_waitq);
|
||||
group->q_len = 0;
|
||||
group->max_events = UINT_MAX;
|
||||
|
||||
spin_lock_init(&group->mark_lock);
|
||||
atomic_set(&group->num_marks, 0);
|
||||
INIT_LIST_HEAD(&group->mark_entries);
|
||||
|
|
|
|||
|
|
@ -16,6 +16,21 @@
|
|||
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
|
||||
*/
|
||||
|
||||
/*
|
||||
* Basic idea behind the notification queue: An fsnotify group (like inotify)
|
||||
* sends the userspace notification about events asyncronously some time after
|
||||
* the event happened. When inotify gets an event it will need to add that
|
||||
* event to the group notify queue. Since a single event might need to be on
|
||||
* multiple group's notification queues we can't add the event directly to each
|
||||
* queue and instead add a small "event_holder" to each queue. This event_holder
|
||||
* has a pointer back to the original event. Since the majority of events are
|
||||
* going to end up on one, and only one, notification queue we embed one
|
||||
* event_holder into each event. This means we have a single allocation instead
|
||||
* of always needing two. If the embedded event_holder is already in use by
|
||||
* another group a new event_holder (from fsnotify_event_holder_cachep) will be
|
||||
* allocated and used.
|
||||
*/
|
||||
|
||||
#include <linux/fs.h>
|
||||
#include <linux/init.h>
|
||||
#include <linux/kernel.h>
|
||||
|
|
@ -33,6 +48,21 @@
|
|||
#include "fsnotify.h"
|
||||
|
||||
static struct kmem_cache *fsnotify_event_cachep;
|
||||
static struct kmem_cache *fsnotify_event_holder_cachep;
|
||||
/*
|
||||
* This is a magic event we send when the q is too full. Since it doesn't
|
||||
* hold real event information we just keep one system wide and use it any time
|
||||
* it is needed. It's refcnt is set 1 at kernel init time and will never
|
||||
* get set to 0 so it will never get 'freed'
|
||||
*/
|
||||
static struct fsnotify_event q_overflow_event;
|
||||
|
||||
/* return true if the notify queue is empty, false otherwise */
|
||||
bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
|
||||
{
|
||||
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
||||
return list_empty(&group->notification_list) ? true : false;
|
||||
}
|
||||
|
||||
void fsnotify_get_event(struct fsnotify_event *event)
|
||||
{
|
||||
|
|
@ -52,9 +82,198 @@ void fsnotify_put_event(struct fsnotify_event *event)
|
|||
}
|
||||
}
|
||||
|
||||
struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
|
||||
{
|
||||
return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
|
||||
}
|
||||
|
||||
void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
|
||||
{
|
||||
kmem_cache_free(fsnotify_event_holder_cachep, holder);
|
||||
}
|
||||
|
||||
/*
|
||||
* Allocate a new event which will be sent to each group's handle_event function
|
||||
* if the group was interested in this particular event.
|
||||
* check if 2 events contain the same information.
|
||||
*/
|
||||
static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
|
||||
{
|
||||
if ((old->mask == new->mask) &&
|
||||
(old->to_tell == new->to_tell) &&
|
||||
(old->data_type == new->data_type)) {
|
||||
switch (old->data_type) {
|
||||
case (FSNOTIFY_EVENT_INODE):
|
||||
if (old->inode == new->inode)
|
||||
return true;
|
||||
break;
|
||||
case (FSNOTIFY_EVENT_PATH):
|
||||
if ((old->path.mnt == new->path.mnt) &&
|
||||
(old->path.dentry == new->path.dentry))
|
||||
return true;
|
||||
case (FSNOTIFY_EVENT_NONE):
|
||||
return true;
|
||||
};
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
/*
|
||||
* Add an event to the group notification queue. The group can later pull this
|
||||
* 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)
|
||||
{
|
||||
struct fsnotify_event_holder *holder = NULL;
|
||||
struct list_head *list = &group->notification_list;
|
||||
struct fsnotify_event_holder *last_holder;
|
||||
struct fsnotify_event *last_event;
|
||||
|
||||
/*
|
||||
* 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
|
||||
* holder.
|
||||
* For the overflow event it's possible that something will use the in
|
||||
* event holder before we get the lock so we may need to jump back and
|
||||
* alloc a new holder, this can't happen for most events...
|
||||
*/
|
||||
if (!list_empty(&event->holder.event_list)) {
|
||||
alloc_holder:
|
||||
holder = fsnotify_alloc_event_holder();
|
||||
if (!holder)
|
||||
return -ENOMEM;
|
||||
}
|
||||
|
||||
mutex_lock(&group->notification_mutex);
|
||||
|
||||
if (group->q_len >= group->max_events)
|
||||
event = &q_overflow_event;
|
||||
|
||||
spin_lock(&event->lock);
|
||||
|
||||
if (list_empty(&event->holder.event_list)) {
|
||||
if (unlikely(holder))
|
||||
fsnotify_destroy_event_holder(holder);
|
||||
holder = &event->holder;
|
||||
} else if (unlikely(!holder)) {
|
||||
/* between the time we checked above and got the lock the in
|
||||
* event holder was used, go back and get a new one */
|
||||
spin_unlock(&event->lock);
|
||||
mutex_unlock(&group->notification_mutex);
|
||||
goto alloc_holder;
|
||||
}
|
||||
|
||||
if (!list_empty(list)) {
|
||||
last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
|
||||
last_event = last_holder->event;
|
||||
if (event_compare(last_event, event)) {
|
||||
spin_unlock(&event->lock);
|
||||
mutex_unlock(&group->notification_mutex);
|
||||
if (holder != &event->holder)
|
||||
fsnotify_destroy_event_holder(holder);
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
group->q_len++;
|
||||
holder->event = event;
|
||||
|
||||
fsnotify_get_event(event);
|
||||
list_add_tail(&holder->event_list, list);
|
||||
spin_unlock(&event->lock);
|
||||
mutex_unlock(&group->notification_mutex);
|
||||
|
||||
wake_up(&group->notification_waitq);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Remove and return the first event from the notification list. There is a
|
||||
* reference held on this event since it was on the list. It is the responsibility
|
||||
* of the caller to drop this reference.
|
||||
*/
|
||||
struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group)
|
||||
{
|
||||
struct fsnotify_event *event;
|
||||
struct fsnotify_event_holder *holder;
|
||||
|
||||
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
||||
|
||||
holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
|
||||
|
||||
event = holder->event;
|
||||
|
||||
spin_lock(&event->lock);
|
||||
holder->event = NULL;
|
||||
list_del_init(&holder->event_list);
|
||||
spin_unlock(&event->lock);
|
||||
|
||||
/* event == holder means we are referenced through the in event holder */
|
||||
if (holder != &event->holder)
|
||||
fsnotify_destroy_event_holder(holder);
|
||||
|
||||
group->q_len--;
|
||||
|
||||
return event;
|
||||
}
|
||||
|
||||
/*
|
||||
* This will not remove the event, that must be done with fsnotify_remove_notify_event()
|
||||
*/
|
||||
struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group)
|
||||
{
|
||||
struct fsnotify_event *event;
|
||||
struct fsnotify_event_holder *holder;
|
||||
|
||||
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
||||
|
||||
holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
|
||||
event = holder->event;
|
||||
|
||||
return event;
|
||||
}
|
||||
|
||||
/*
|
||||
* Called when a group is being torn down to clean up any outstanding
|
||||
* event notifications.
|
||||
*/
|
||||
void fsnotify_flush_notify(struct fsnotify_group *group)
|
||||
{
|
||||
struct fsnotify_event *event;
|
||||
|
||||
mutex_lock(&group->notification_mutex);
|
||||
while (!fsnotify_notify_queue_is_empty(group)) {
|
||||
event = fsnotify_remove_notify_event(group);
|
||||
fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
|
||||
}
|
||||
mutex_unlock(&group->notification_mutex);
|
||||
}
|
||||
|
||||
static void initialize_event(struct fsnotify_event *event)
|
||||
{
|
||||
event->holder.event = NULL;
|
||||
INIT_LIST_HEAD(&event->holder.event_list);
|
||||
atomic_set(&event->refcnt, 1);
|
||||
|
||||
spin_lock_init(&event->lock);
|
||||
|
||||
event->path.dentry = NULL;
|
||||
event->path.mnt = NULL;
|
||||
event->inode = NULL;
|
||||
event->data_type = FSNOTIFY_EVENT_NONE;
|
||||
|
||||
event->to_tell = NULL;
|
||||
}
|
||||
|
||||
/*
|
||||
* 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
|
||||
* particular event.
|
||||
*
|
||||
* @to_tell the inode which is supposed to receive the event (sometimes a
|
||||
* parent of the inode to which the event happened.
|
||||
* @mask what actually happened.
|
||||
* @data pointer to the object which was actually affected
|
||||
* @data_type flag indication if the data is a file, path, inode, nothing...
|
||||
*/
|
||||
struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
|
||||
void *data, int data_type)
|
||||
|
|
@ -65,14 +284,7 @@ struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
|
|||
if (!event)
|
||||
return NULL;
|
||||
|
||||
atomic_set(&event->refcnt, 1);
|
||||
|
||||
spin_lock_init(&event->lock);
|
||||
|
||||
event->path.dentry = NULL;
|
||||
event->path.mnt = NULL;
|
||||
event->inode = NULL;
|
||||
|
||||
initialize_event(event);
|
||||
event->to_tell = to_tell;
|
||||
|
||||
switch (data_type) {
|
||||
|
|
@ -114,6 +326,10 @@ struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
|
|||
__init int fsnotify_notification_init(void)
|
||||
{
|
||||
fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
|
||||
fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
|
||||
|
||||
initialize_event(&q_overflow_event);
|
||||
q_overflow_event.mask = FS_Q_OVERFLOW;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -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 */
|
||||
|
|
|
|||
Loading…
Reference in New Issue