LXR linux/fs/notify/group.c

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
   4 */
   5
   6#include <linux/list.h>
   7#include <linux/mutex.h>
   8#include <linux/slab.h>
   9#include <linux/srcu.h>
  10#include <linux/rculist.h>
  11#include <linux/wait.h>
  12#include <linux/memcontrol.h>
  13
  14#include <linux/fsnotify_backend.h>
  15#include "fsnotify.h"
  16
  17#include <linux/atomic.h>
  18
  19/*
  20 * Final freeing of a group
  21 */
  22static void fsnotify_final_destroy_group(struct fsnotify_group *group)
  23{
  24        if (group->ops->free_group_priv)
  25                group->ops->free_group_priv(group);
  26
  27        mem_cgroup_put(group->memcg);
  28        mutex_destroy(&group->mark_mutex);
  29
  30        kfree(group);
  31}
  32
  33/*
  34 * Stop queueing new events for this group. Once this function returns
  35 * fsnotify_add_event() will not add any new events to the group's queue.
  36 */
  37void fsnotify_group_stop_queueing(struct fsnotify_group *group)
  38{
  39        spin_lock(&group->notification_lock);
  40        group->shutdown = true;
  41        spin_unlock(&group->notification_lock);
  42}
  43
  44/*
  45 * Trying to get rid of a group. Remove all marks, flush all events and release
  46 * the group reference.
  47 * Note that another thread calling fsnotify_clear_marks_by_group() may still
  48 * hold a ref to the group.
  49 */
  50void fsnotify_destroy_group(struct fsnotify_group *group)
  51{
  52        /*
  53         * Stop queueing new events. The code below is careful enough to not
  54         * require this but fanotify needs to stop queuing events even before
  55         * fsnotify_destroy_group() is called and this makes the other callers
  56         * of fsnotify_destroy_group() to see the same behavior.
  57         */
  58        fsnotify_group_stop_queueing(group);
  59
  60        /* Clear all marks for this group and queue them for destruction */
  61        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK);
  62
  63        /*
  64         * Some marks can still be pinned when waiting for response from
  65         * userspace. Wait for those now. fsnotify_prepare_user_wait() will
  66         * not succeed now so this wait is race-free.
  67         */
  68        wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
  69
  70        /*
  71         * Wait until all marks get really destroyed. We could actually destroy
  72         * them ourselves instead of waiting for worker to do it, however that
  73         * would be racy as worker can already be processing some marks before
  74         * we even entered fsnotify_destroy_group().
  75         */
  76        fsnotify_wait_marks_destroyed();
  77
  78        /*
  79         * Since we have waited for fsnotify_mark_srcu in
  80         * fsnotify_mark_destroy_list() there can be no outstanding event
  81         * notification against this group. So clearing the notification queue
  82         * of all events is reliable now.
  83         */
  84        fsnotify_flush_notify(group);
  85
  86        /*
  87         * Destroy overflow event (we cannot use fsnotify_destroy_event() as
  88         * that deliberately ignores overflow events.
  89         */
  90        if (group->overflow_event)
  91                group->ops->free_event(group->overflow_event);
  92
  93        fsnotify_put_group(group);
  94}
  95
  96/*
  97 * Get reference to a group.
  98 */
  99void fsnotify_get_group(struct fsnotify_group *group)
 100{
 101        refcount_inc(&group->refcnt);
 102}
 103
 104/*
 105 * Drop a reference to a group.  Free it if it's through.
 106 */
 107void fsnotify_put_group(struct fsnotify_group *group)
 108{
 109        if (refcount_dec_and_test(&group->refcnt))
 110                fsnotify_final_destroy_group(group);
 111}
 112EXPORT_SYMBOL_GPL(fsnotify_put_group);
 113
 114/*
 115 * Create a new fsnotify_group and hold a reference for the group returned.
 116 */
 117struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
 118{
 119        struct fsnotify_group *group;
 120
 121        group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
 122        if (!group)
 123                return ERR_PTR(-ENOMEM);
 124
 125        /* set to 0 when there a no external references to this group */
 126        refcount_set(&group->refcnt, 1);
 127        atomic_set(&group->num_marks, 0);
 128        atomic_set(&group->user_waits, 0);
 129
 130        spin_lock_init(&group->notification_lock);
 131        INIT_LIST_HEAD(&group->notification_list);
 132        init_waitqueue_head(&group->notification_waitq);
 133        group->max_events = UINT_MAX;
 134
 135        mutex_init(&group->mark_mutex);
 136        INIT_LIST_HEAD(&group->marks_list);
 137
 138        group->ops = ops;
 139
 140        return group;
 141}
 142EXPORT_SYMBOL_GPL(fsnotify_alloc_group);
 143
 144int fsnotify_fasync(int fd, struct file *file, int on)
 145{
 146        struct fsnotify_group *group = file->private_data;
 147
 148        return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
 149}
 150