mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
189 lines
5.6 KiB
189 lines
5.6 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
|
/* |
|
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <[email protected]> |
|
*/ |
|
|
|
/* |
|
* Basic idea behind the notification queue: An fsnotify group (like inotify) |
|
* sends the userspace notification about events asynchronously 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> |
|
#include <linux/list.h> |
|
#include <linux/module.h> |
|
#include <linux/mount.h> |
|
#include <linux/mutex.h> |
|
#include <linux/namei.h> |
|
#include <linux/path.h> |
|
#include <linux/slab.h> |
|
#include <linux/spinlock.h> |
|
|
|
#include <linux/atomic.h> |
|
|
|
#include <linux/fsnotify_backend.h> |
|
#include "fsnotify.h" |
|
|
|
static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0); |
|
|
|
/** |
|
* fsnotify_get_cookie - return a unique cookie for use in synchronizing events. |
|
* Called from fsnotify_move, which is inlined into filesystem modules. |
|
*/ |
|
u32 fsnotify_get_cookie(void) |
|
{ |
|
return atomic_inc_return(&fsnotify_sync_cookie); |
|
} |
|
EXPORT_SYMBOL_GPL(fsnotify_get_cookie); |
|
|
|
/* return true if the notify queue is empty, false otherwise */ |
|
bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group) |
|
{ |
|
assert_spin_locked(&group->notification_lock); |
|
return list_empty(&group->notification_list) ? true : false; |
|
} |
|
|
|
void fsnotify_destroy_event(struct fsnotify_group *group, |
|
struct fsnotify_event *event) |
|
{ |
|
/* Overflow events are per-group and we don't want to free them */ |
|
if (!event || event == group->overflow_event) |
|
return; |
|
/* |
|
* If the event is still queued, we have a problem... Do an unreliable |
|
* lockless check first to avoid locking in the common case. The |
|
* locking may be necessary for permission events which got removed |
|
* from the list by a different CPU than the one freeing the event. |
|
*/ |
|
if (!list_empty(&event->list)) { |
|
spin_lock(&group->notification_lock); |
|
WARN_ON(!list_empty(&event->list)); |
|
spin_unlock(&group->notification_lock); |
|
} |
|
group->ops->free_event(event); |
|
} |
|
|
|
/* |
|
* Add an event to the group notification queue. The group can later pull this |
|
* event off the queue to deal with. The function returns 0 if the event was |
|
* added to the queue, 1 if the event was merged with some other queued event, |
|
* 2 if the event was not queued - either the queue of events has overflown |
|
* or the group is shutting down. |
|
*/ |
|
int fsnotify_add_event(struct fsnotify_group *group, |
|
struct fsnotify_event *event, |
|
int (*merge)(struct list_head *, |
|
struct fsnotify_event *)) |
|
{ |
|
int ret = 0; |
|
struct list_head *list = &group->notification_list; |
|
|
|
pr_debug("%s: group=%p event=%p\n", __func__, group, event); |
|
|
|
spin_lock(&group->notification_lock); |
|
|
|
if (group->shutdown) { |
|
spin_unlock(&group->notification_lock); |
|
return 2; |
|
} |
|
|
|
if (event == group->overflow_event || |
|
group->q_len >= group->max_events) { |
|
ret = 2; |
|
/* Queue overflow event only if it isn't already queued */ |
|
if (!list_empty(&group->overflow_event->list)) { |
|
spin_unlock(&group->notification_lock); |
|
return ret; |
|
} |
|
event = group->overflow_event; |
|
goto queue; |
|
} |
|
|
|
if (!list_empty(list) && merge) { |
|
ret = merge(list, event); |
|
if (ret) { |
|
spin_unlock(&group->notification_lock); |
|
return ret; |
|
} |
|
} |
|
|
|
queue: |
|
group->q_len++; |
|
list_add_tail(&event->list, list); |
|
spin_unlock(&group->notification_lock); |
|
|
|
wake_up(&group->notification_waitq); |
|
kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); |
|
return ret; |
|
} |
|
|
|
void fsnotify_remove_queued_event(struct fsnotify_group *group, |
|
struct fsnotify_event *event) |
|
{ |
|
assert_spin_locked(&group->notification_lock); |
|
/* |
|
* We need to init list head for the case of overflow event so that |
|
* check in fsnotify_add_event() works |
|
*/ |
|
list_del_init(&event->list); |
|
group->q_len--; |
|
} |
|
|
|
/* |
|
* Remove and return the first event from the notification list. It is the |
|
* responsibility of the caller to destroy the obtained event |
|
*/ |
|
struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group) |
|
{ |
|
struct fsnotify_event *event; |
|
|
|
assert_spin_locked(&group->notification_lock); |
|
|
|
pr_debug("%s: group=%p\n", __func__, group); |
|
|
|
event = list_first_entry(&group->notification_list, |
|
struct fsnotify_event, list); |
|
fsnotify_remove_queued_event(group, event); |
|
return event; |
|
} |
|
|
|
/* |
|
* This will not remove the event, that must be done with |
|
* fsnotify_remove_first_event() |
|
*/ |
|
struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) |
|
{ |
|
assert_spin_locked(&group->notification_lock); |
|
|
|
return list_first_entry(&group->notification_list, |
|
struct fsnotify_event, list); |
|
} |
|
|
|
/* |
|
* 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; |
|
|
|
spin_lock(&group->notification_lock); |
|
while (!fsnotify_notify_queue_is_empty(group)) { |
|
event = fsnotify_remove_first_event(group); |
|
spin_unlock(&group->notification_lock); |
|
fsnotify_destroy_event(group, event); |
|
spin_lock(&group->notification_lock); |
|
} |
|
spin_unlock(&group->notification_lock); |
|
}
|
|
|