Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 189 insertions, 0 deletions

diff --git a/fs/notify/notification.c b/fs/notify/notification.c
new file mode 100644
index 000000000..75d79d6d3
--- /dev/null
+++ b/fs/notify/notification.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
+ */
+
+/*
+ * 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);
+}