Line data    Source code

       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             :  */
      22           7 : static void fsnotify_final_destroy_group(struct fsnotify_group *group)
      23             : {
      24           7 :         if (group->ops->free_group_priv)
      25           7 :                 group->ops->free_group_priv(group);
      26             : 
      27           7 :         mem_cgroup_put(group->memcg);
      28           7 :         mutex_destroy(&group->mark_mutex);
      29             : 
      30           7 :         kfree(group);
      31           7 : }
      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             :  */
      37           7 : void fsnotify_group_stop_queueing(struct fsnotify_group *group)
      38             : {
      39           7 :         spin_lock(&group->notification_lock);
      40           7 :         group->shutdown = true;
      41           7 :         spin_unlock(&group->notification_lock);
      42           7 : }
      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             :  */
      50           7 : void 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           7 :         fsnotify_group_stop_queueing(group);
      59             : 
      60             :         /* Clear all marks for this group and queue them for destruction */
      61           7 :         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           7 :         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           7 :         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           7 :         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           7 :         if (group->overflow_event)
      91           7 :                 group->ops->free_event(group->overflow_event);
      92             : 
      93           7 :         fsnotify_put_group(group);
      94           7 : }
      95             : 
      96             : /*
      97             :  * Get reference to a group.
      98             :  */
      99          86 : void fsnotify_get_group(struct fsnotify_group *group)
     100             : {
     101          86 :         refcount_inc(&group->refcnt);
     102          86 : }
     103             : 
     104             : /*
     105             :  * Drop a reference to a group.  Free it if it's through.
     106             :  */
     107          44 : void fsnotify_put_group(struct fsnotify_group *group)
     108             : {
     109          44 :         if (refcount_dec_and_test(&group->refcnt))
     110           7 :                 fsnotify_final_destroy_group(group);
     111          44 : }
     112             : EXPORT_SYMBOL_GPL(fsnotify_put_group);
     113             : 
     114          20 : static struct fsnotify_group *__fsnotify_alloc_group(
     115             :                                 const struct fsnotify_ops *ops, gfp_t gfp)
     116             : {
     117          20 :         struct fsnotify_group *group;
     118             : 
     119          20 :         group = kzalloc(sizeof(struct fsnotify_group), gfp);
     120          20 :         if (!group)
     121          20 :                 return ERR_PTR(-ENOMEM);
     122             : 
     123             :         /* set to 0 when there a no external references to this group */
     124          20 :         refcount_set(&group->refcnt, 1);
     125          20 :         atomic_set(&group->num_marks, 0);
     126          20 :         atomic_set(&group->user_waits, 0);
     127             : 
     128          20 :         spin_lock_init(&group->notification_lock);
     129          20 :         INIT_LIST_HEAD(&group->notification_list);
     130          20 :         init_waitqueue_head(&group->notification_waitq);
     131          20 :         group->max_events = UINT_MAX;
     132             : 
     133          20 :         mutex_init(&group->mark_mutex);
     134          20 :         INIT_LIST_HEAD(&group->marks_list);
     135             : 
     136          20 :         group->ops = ops;
     137             : 
     138          20 :         return group;
     139             : }
     140             : 
     141             : /*
     142             :  * Create a new fsnotify_group and hold a reference for the group returned.
     143             :  */
     144           0 : struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
     145             : {
     146           0 :         return __fsnotify_alloc_group(ops, GFP_KERNEL);
     147             : }
     148             : EXPORT_SYMBOL_GPL(fsnotify_alloc_group);
     149             : 
     150             : /*
     151             :  * Create a new fsnotify_group and hold a reference for the group returned.
     152             :  */
     153          20 : struct fsnotify_group *fsnotify_alloc_user_group(const struct fsnotify_ops *ops)
     154             : {
     155          20 :         return __fsnotify_alloc_group(ops, GFP_KERNEL_ACCOUNT);
     156             : }
     157             : EXPORT_SYMBOL_GPL(fsnotify_alloc_user_group);
     158             : 
     159           0 : int fsnotify_fasync(int fd, struct file *file, int on)
     160             : {
     161           0 :         struct fsnotify_group *group = file->private_data;
     162             : 
     163           0 :         return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
     164             : }