fs/notify/group.c

   1 /*
   2  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
   3  *
   4  *  This program is free software; you can redistribute it and/or modify
   5  *  it under the terms of the GNU General Public License as published by
   6  *  the Free Software Foundation; either version 2, or (at your option)
   7  *  any later version.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License
  15  *  along with this program; see the file COPYING.  If not, write to
  16  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <linux/list.h>
  20 #include <linux/mutex.h>
  21 #include <linux/slab.h>
  22 #include <linux/srcu.h>
  23 #include <linux/rculist.h>
  24 #include <linux/wait.h>
  25
  26 #include <linux/fsnotify_backend.h>
  27 #include "fsnotify.h"
  28
  29 #include <linux/atomic.h>
  30
  31 /*
  32  * Final freeing of a group
  33  */
  34 static void fsnotify_final_destroy_group(struct fsnotify_group *group)
  35 {
  36         if (group->ops->free_group_priv)
  37                 group->ops->free_group_priv(group);
  38
  39         kfree(group);
  40 }
  41
  42 /*
  43  * Trying to get rid of a group. Remove all marks, flush all events and release
  44  * the group reference.
  45  * Note that another thread calling fsnotify_clear_marks_by_group() may still
  46  * hold a ref to the group.
  47  */
  48 void fsnotify_destroy_group(struct fsnotify_group *group)
  49 {
  50         /* clear all inode marks for this group */
  51         fsnotify_clear_marks_by_group(group);
  52
  53         synchronize_srcu(&fsnotify_mark_srcu);
  54
  55         /* clear the notification queue of all events */
  56         fsnotify_flush_notify(group);
  57
  58         /*
  59          * Destroy overflow event (we cannot use fsnotify_destroy_event() as
  60          * that deliberately ignores overflow events.
  61          */
  62         if (group->overflow_event)
  63                 group->ops->free_event(group->overflow_event);
  64
  65         fsnotify_put_group(group);
  66 }
  67
  68 /*
  69  * Get reference to a group.
  70  */
  71 void fsnotify_get_group(struct fsnotify_group *group)
  72 {
  73         atomic_inc(&group->refcnt);
  74 }
  75
  76 /*
  77  * Drop a reference to a group.  Free it if it's through.
  78  */
  79 void fsnotify_put_group(struct fsnotify_group *group)
  80 {
  81         if (atomic_dec_and_test(&group->refcnt))
  82                 fsnotify_final_destroy_group(group);
  83 }
  84
  85 /*
  86  * Create a new fsnotify_group and hold a reference for the group returned.
  87  */
  88 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
  89 {
  90         struct fsnotify_group *group;
  91
  92         group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
  93         if (!group)
  94                 return ERR_PTR(-ENOMEM);
  95
  96         /* set to 0 when there a no external references to this group */
  97         atomic_set(&group->refcnt, 1);
  98         atomic_set(&group->num_marks, 0);
  99
 100         mutex_init(&group->notification_mutex);
 101         INIT_LIST_HEAD(&group->notification_list);
 102         init_waitqueue_head(&group->notification_waitq);
 103         group->max_events = UINT_MAX;
 104
 105         mutex_init(&group->mark_mutex);
 106         INIT_LIST_HEAD(&group->marks_list);
 107
 108         group->ops = ops;
 109
 110         return group;
 111 }
 112
 113 int fsnotify_fasync(int fd, struct file *file, int on)
 114 {
 115         struct fsnotify_group *group = file->private_data;
 116
 117         return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
 118 }