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![Thomas Gleixner](/assets/img/avatar_default.png)
Based on 1 normalized pattern(s): 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 extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 52 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com> Reviewed-by: Steve Winslow <swinslow@gmail.com> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190519154042.342335923@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
189 lines
5.6 KiB
C
189 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*/
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/*
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* Basic idea behind the notification queue: An fsnotify group (like inotify)
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* sends the userspace notification about events asynchronously some time after
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* the event happened. When inotify gets an event it will need to add that
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* event to the group notify queue. Since a single event might need to be on
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* multiple group's notification queues we can't add the event directly to each
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* queue and instead add a small "event_holder" to each queue. This event_holder
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* has a pointer back to the original event. Since the majority of events are
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* going to end up on one, and only one, notification queue we embed one
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* event_holder into each event. This means we have a single allocation instead
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* of always needing two. If the embedded event_holder is already in use by
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* another group a new event_holder (from fsnotify_event_holder_cachep) will be
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* allocated and used.
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*/
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/mutex.h>
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#include <linux/namei.h>
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#include <linux/path.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/atomic.h>
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0);
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/**
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* fsnotify_get_cookie - return a unique cookie for use in synchronizing events.
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* Called from fsnotify_move, which is inlined into filesystem modules.
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*/
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u32 fsnotify_get_cookie(void)
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{
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return atomic_inc_return(&fsnotify_sync_cookie);
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}
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EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
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/* return true if the notify queue is empty, false otherwise */
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bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
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{
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assert_spin_locked(&group->notification_lock);
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return list_empty(&group->notification_list) ? true : false;
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}
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void fsnotify_destroy_event(struct fsnotify_group *group,
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struct fsnotify_event *event)
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{
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/* Overflow events are per-group and we don't want to free them */
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if (!event || event == group->overflow_event)
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return;
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/*
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* If the event is still queued, we have a problem... Do an unreliable
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* lockless check first to avoid locking in the common case. The
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* locking may be necessary for permission events which got removed
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* from the list by a different CPU than the one freeing the event.
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*/
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if (!list_empty(&event->list)) {
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spin_lock(&group->notification_lock);
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WARN_ON(!list_empty(&event->list));
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spin_unlock(&group->notification_lock);
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}
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group->ops->free_event(event);
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}
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/*
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* Add an event to the group notification queue. The group can later pull this
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* event off the queue to deal with. The function returns 0 if the event was
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* added to the queue, 1 if the event was merged with some other queued event,
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* 2 if the event was not queued - either the queue of events has overflown
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* or the group is shutting down.
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*/
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int fsnotify_add_event(struct fsnotify_group *group,
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struct fsnotify_event *event,
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int (*merge)(struct list_head *,
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struct fsnotify_event *))
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{
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int ret = 0;
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struct list_head *list = &group->notification_list;
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pr_debug("%s: group=%p event=%p\n", __func__, group, event);
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spin_lock(&group->notification_lock);
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if (group->shutdown) {
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spin_unlock(&group->notification_lock);
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return 2;
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}
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if (event == group->overflow_event ||
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group->q_len >= group->max_events) {
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ret = 2;
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/* Queue overflow event only if it isn't already queued */
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if (!list_empty(&group->overflow_event->list)) {
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spin_unlock(&group->notification_lock);
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return ret;
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}
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event = group->overflow_event;
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goto queue;
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}
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if (!list_empty(list) && merge) {
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ret = merge(list, event);
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if (ret) {
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spin_unlock(&group->notification_lock);
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return ret;
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}
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}
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queue:
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group->q_len++;
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list_add_tail(&event->list, list);
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spin_unlock(&group->notification_lock);
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wake_up(&group->notification_waitq);
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kill_fasync(&group->fsn_fa, SIGIO, POLL_IN);
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return ret;
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}
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void fsnotify_remove_queued_event(struct fsnotify_group *group,
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struct fsnotify_event *event)
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{
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assert_spin_locked(&group->notification_lock);
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/*
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* We need to init list head for the case of overflow event so that
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* check in fsnotify_add_event() works
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*/
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list_del_init(&event->list);
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group->q_len--;
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}
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/*
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* Remove and return the first event from the notification list. It is the
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* responsibility of the caller to destroy the obtained event
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*/
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struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)
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{
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struct fsnotify_event *event;
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assert_spin_locked(&group->notification_lock);
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pr_debug("%s: group=%p\n", __func__, group);
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event = list_first_entry(&group->notification_list,
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struct fsnotify_event, list);
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fsnotify_remove_queued_event(group, event);
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return event;
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}
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/*
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* This will not remove the event, that must be done with
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* fsnotify_remove_first_event()
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*/
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struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group)
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{
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assert_spin_locked(&group->notification_lock);
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return list_first_entry(&group->notification_list,
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struct fsnotify_event, list);
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}
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/*
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* Called when a group is being torn down to clean up any outstanding
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* event notifications.
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*/
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void fsnotify_flush_notify(struct fsnotify_group *group)
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{
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struct fsnotify_event *event;
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spin_lock(&group->notification_lock);
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while (!fsnotify_notify_queue_is_empty(group)) {
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event = fsnotify_remove_first_event(group);
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spin_unlock(&group->notification_lock);
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fsnotify_destroy_event(group, event);
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spin_lock(&group->notification_lock);
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}
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spin_unlock(&group->notification_lock);
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}
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