// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> */ #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); mutex_destroy(&group->mark_mutex); 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); } EXPORT_SYMBOL_GPL(fsnotify_put_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; } EXPORT_SYMBOL_GPL(fsnotify_alloc_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; }