v4.19.13 snapshot.
diff --git a/fs/notify/group.c b/fs/notify/group.c
new file mode 100644
index 0000000..c03b836
--- /dev/null
+++ b/fs/notify/group.c
@@ -0,0 +1,159 @@
+/*
+ * 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.
+ */
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/srcu.h>
+#include <linux/rculist.h>
+#include <linux/wait.h>
+#include <linux/memcontrol.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+#include <linux/atomic.h>
+
+/*
+ * Final freeing of a group
+ */
+static void fsnotify_final_destroy_group(struct fsnotify_group *group)
+{
+ if (group->ops->free_group_priv)
+ group->ops->free_group_priv(group);
+
+ mem_cgroup_put(group->memcg);
+
+ kfree(group);
+}
+
+/*
+ * Stop queueing new events for this group. Once this function returns
+ * fsnotify_add_event() will not add any new events to the group's queue.
+ */
+void fsnotify_group_stop_queueing(struct fsnotify_group *group)
+{
+ spin_lock(&group->notification_lock);
+ group->shutdown = true;
+ spin_unlock(&group->notification_lock);
+}
+
+/*
+ * Trying to get rid of a group. Remove all marks, flush all events and release
+ * the group reference.
+ * Note that another thread calling fsnotify_clear_marks_by_group() may still
+ * hold a ref to the group.
+ */
+void fsnotify_destroy_group(struct fsnotify_group *group)
+{
+ /*
+ * Stop queueing new events. The code below is careful enough to not
+ * require this but fanotify needs to stop queuing events even before
+ * fsnotify_destroy_group() is called and this makes the other callers
+ * of fsnotify_destroy_group() to see the same behavior.
+ */
+ fsnotify_group_stop_queueing(group);
+
+ /* Clear all marks for this group and queue them for destruction */
+ fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK);
+
+ /*
+ * Some marks can still be pinned when waiting for response from
+ * userspace. Wait for those now. fsnotify_prepare_user_wait() will
+ * not succeed now so this wait is race-free.
+ */
+ wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
+
+ /*
+ * Wait until all marks get really destroyed. We could actually destroy
+ * them ourselves instead of waiting for worker to do it, however that
+ * would be racy as worker can already be processing some marks before
+ * we even entered fsnotify_destroy_group().
+ */
+ fsnotify_wait_marks_destroyed();
+
+ /*
+ * Since we have waited for fsnotify_mark_srcu in
+ * fsnotify_mark_destroy_list() there can be no outstanding event
+ * notification against this group. So clearing the notification queue
+ * of all events is reliable now.
+ */
+ fsnotify_flush_notify(group);
+
+ /*
+ * Destroy overflow event (we cannot use fsnotify_destroy_event() as
+ * that deliberately ignores overflow events.
+ */
+ if (group->overflow_event)
+ group->ops->free_event(group->overflow_event);
+
+ fsnotify_put_group(group);
+}
+
+/*
+ * Get reference to a group.
+ */
+void fsnotify_get_group(struct fsnotify_group *group)
+{
+ refcount_inc(&group->refcnt);
+}
+
+/*
+ * Drop a reference to a group. Free it if it's through.
+ */
+void fsnotify_put_group(struct fsnotify_group *group)
+{
+ if (refcount_dec_and_test(&group->refcnt))
+ fsnotify_final_destroy_group(group);
+}
+
+/*
+ * Create a new fsnotify_group and hold a reference for the group returned.
+ */
+struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
+{
+ struct fsnotify_group *group;
+
+ group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
+ if (!group)
+ return ERR_PTR(-ENOMEM);
+
+ /* set to 0 when there a no external references to this group */
+ refcount_set(&group->refcnt, 1);
+ atomic_set(&group->num_marks, 0);
+ atomic_set(&group->user_waits, 0);
+
+ spin_lock_init(&group->notification_lock);
+ INIT_LIST_HEAD(&group->notification_list);
+ init_waitqueue_head(&group->notification_waitq);
+ group->max_events = UINT_MAX;
+
+ mutex_init(&group->mark_mutex);
+ INIT_LIST_HEAD(&group->marks_list);
+
+ group->ops = ops;
+
+ return group;
+}
+
+int fsnotify_fasync(int fd, struct file *file, int on)
+{
+ struct fsnotify_group *group = file->private_data;
+
+ return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
+}