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Diffstat (limited to 'kernel/fs/notify/notification.c')
| -rw-r--r-- | kernel/fs/notify/notification.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/kernel/fs/notify/notification.c b/kernel/fs/notify/notification.c new file mode 100644 index 000000000..a95d8e037 --- /dev/null +++ b/kernel/fs/notify/notification.c @@ -0,0 +1,213 @@ +/* + * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2, or (at your option) + * any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; see the file COPYING. If not, write to + * 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 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) +{ + BUG_ON(!mutex_is_locked(&group->notification_mutex)); + 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->mask == FS_Q_OVERFLOW) + return; + /* If the event is still queued, we have a problem... */ + WARN_ON(!list_empty(&event->list)); + 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 queue of events has overflown. + */ +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); + + mutex_lock(&group->notification_mutex); + + if (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)) { + mutex_unlock(&group->notification_mutex); + return ret; + } + event = group->overflow_event; + goto queue; + } + + if (!list_empty(list) && merge) { + ret = merge(list, event); + if (ret) { + mutex_unlock(&group->notification_mutex); + return ret; + } + } + +queue: + group->q_len++; + list_add_tail(&event->list, list); + mutex_unlock(&group->notification_mutex); + + wake_up(&group->notification_waitq); + kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); + return ret; +} + +/* + * Remove @event from group's notification queue. It is the responsibility of + * the caller to destroy the event. + */ +void fsnotify_remove_event(struct fsnotify_group *group, + struct fsnotify_event *event) +{ + mutex_lock(&group->notification_mutex); + if (!list_empty(&event->list)) { + list_del_init(&event->list); + group->q_len--; + } + mutex_unlock(&group->notification_mutex); +} + +/* + * 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; + + BUG_ON(!mutex_is_locked(&group->notification_mutex)); + + pr_debug("%s: group=%p\n", __func__, group); + + event = list_first_entry(&group->notification_list, + struct fsnotify_event, list); + /* + * 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--; + + 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) +{ + BUG_ON(!mutex_is_locked(&group->notification_mutex)); + + 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; + + mutex_lock(&group->notification_mutex); + while (!fsnotify_notify_queue_is_empty(group)) { + event = fsnotify_remove_first_event(group); + fsnotify_destroy_event(group, event); + } + mutex_unlock(&group->notification_mutex); +} + +/* + * 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. + * + * @inode 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... + * @name the filename, if available + */ +void fsnotify_init_event(struct fsnotify_event *event, struct inode *inode, + u32 mask) +{ + INIT_LIST_HEAD(&event->list); + event->inode = inode; + event->mask = mask; +} |