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 void fsnotify_final_destroy_group(struct fsnotify_group *group)
  35 {
  36         /* clear the notification queue of all events */
  37         fsnotify_flush_notify(group);
  38
  39         if (group->ops->free_group_priv)
  40                 group->ops->free_group_priv(group);
  41
  42         kfree(group);
  43 }
  44
  45 /*
  46  * Trying to get rid of a group.  We need to first get rid of any outstanding
  47  * allocations and then free the group.  Remember that fsnotify_clear_marks_by_group
  48  * could miss marks that are being freed by inode and those marks could still
  49  * hold a reference to this group (via group->num_marks)  If we get into that
  50  * situtation, the fsnotify_final_destroy_group will get called when that final
  51  * mark is freed.
  52  */
  53 static void fsnotify_destroy_group(struct fsnotify_group *group)
  54 {
  55         /* clear all inode marks for this group */
  56         fsnotify_clear_marks_by_group(group);
  57
  58         synchronize_srcu(&fsnotify_mark_srcu);
  59
  60         /* past the point of no return, matches the initial value of 1 */
  61         if (atomic_dec_and_test(&group->num_marks))
  62                 fsnotify_final_destroy_group(group);
  63 }
  64
  65 /*
  66  * Drop a reference to a group.  Free it if it's through.
  67  */
  68 void fsnotify_put_group(struct fsnotify_group *group)
  69 {
  70         if (atomic_dec_and_test(&group->refcnt))
  71                 fsnotify_destroy_group(group);
  72 }
  73
  74 /*
  75  * Create a new fsnotify_group and hold a reference for the group returned.
  76  */
  77 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
  78 {
  79         struct fsnotify_group *group;
  80
  81         group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
  82         if (!group)
  83                 return ERR_PTR(-ENOMEM);
  84
  85         /* set to 0 when there a no external references to this group */
  86         atomic_set(&group->refcnt, 1);
  87         /*
  88          * hits 0 when there are no external references AND no marks for
  89          * this group
  90          */
  91         atomic_set(&group->num_marks, 1);
  92
  93         mutex_init(&group->notification_mutex);
  94         INIT_LIST_HEAD(&group->notification_list);
  95         init_waitqueue_head(&group->notification_waitq);
  96         group->max_events = UINT_MAX;
  97
  98         spin_lock_init(&group->mark_lock);
  99         INIT_LIST_HEAD(&group->marks_list);
 100
 101         group->ops = ops;
 102
 103         return group;
 104 }