--- /dev/null
+/*
+ * 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;
+}
Code Review / kvmfornfv.git / blobdiff