2 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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)
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.
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.
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>
26 #include <linux/fsnotify_backend.h>
29 #include <asm/atomic.h>
31 /* protects writes to fsnotify_groups and fsnotify_mask */
32 static DEFINE_MUTEX(fsnotify_grp_mutex);
33 /* all groups registered to receive inode filesystem notifications */
34 LIST_HEAD(fsnotify_inode_groups);
35 /* all groups registered to receive mount point filesystem notifications */
36 LIST_HEAD(fsnotify_vfsmount_groups);
39 * Update the group->mask by running all of the marks associated with this
40 * group and finding the bitwise | of all of the mark->mask.
42 void fsnotify_recalc_group_mask(struct fsnotify_group *group)
45 struct fsnotify_mark *mark;
47 spin_lock(&group->mark_lock);
48 list_for_each_entry(mark, &group->marks_list, g_list)
51 spin_unlock(&group->mark_lock);
54 void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
56 struct fsnotify_group *group_iter;
58 mutex_lock(&fsnotify_grp_mutex);
60 if (!group->on_vfsmount_group_list) {
61 list_for_each_entry(group_iter, &fsnotify_vfsmount_groups,
62 vfsmount_group_list) {
63 /* insert in front of this one? */
64 if (group < group_iter) {
65 /* list_add_tail() insert in front of group_iter */
66 list_add_tail_rcu(&group->inode_group_list,
67 &group_iter->inode_group_list);
72 /* apparently we need to be the last entry */
73 list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
76 group->on_vfsmount_group_list = 1;
78 mutex_unlock(&fsnotify_grp_mutex);
81 void fsnotify_add_inode_group(struct fsnotify_group *group)
83 struct fsnotify_group *group_iter;
85 mutex_lock(&fsnotify_grp_mutex);
87 /* add to global group list */
88 if (!group->on_inode_group_list) {
89 list_for_each_entry(group_iter, &fsnotify_inode_groups,
91 if (group < group_iter) {
92 /* list_add_tail() insert in front of group_iter */
93 list_add_tail_rcu(&group->inode_group_list,
94 &group_iter->inode_group_list);
99 /* apparently we need to be the last entry */
100 list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
103 group->on_inode_group_list = 1;
105 mutex_unlock(&fsnotify_grp_mutex);
109 * Final freeing of a group
111 void fsnotify_final_destroy_group(struct fsnotify_group *group)
113 /* clear the notification queue of all events */
114 fsnotify_flush_notify(group);
116 if (group->ops->free_group_priv)
117 group->ops->free_group_priv(group);
123 * Trying to get rid of a group. We need to first get rid of any outstanding
124 * allocations and then free the group. Remember that fsnotify_clear_marks_by_group
125 * could miss marks that are being freed by inode and those marks could still
126 * hold a reference to this group (via group->num_marks) If we get into that
127 * situtation, the fsnotify_final_destroy_group will get called when that final
130 static void fsnotify_destroy_group(struct fsnotify_group *group)
132 /* clear all inode marks for this group */
133 fsnotify_clear_marks_by_group(group);
135 synchronize_srcu(&fsnotify_mark_srcu);
137 /* past the point of no return, matches the initial value of 1 */
138 if (atomic_dec_and_test(&group->num_marks))
139 fsnotify_final_destroy_group(group);
143 * Remove this group from the global list of groups that will get events
144 * this can be done even if there are still references and things still using
145 * this group. This just stops the group from getting new events.
147 static void __fsnotify_evict_group(struct fsnotify_group *group)
149 BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
151 if (group->on_inode_group_list)
152 list_del_rcu(&group->inode_group_list);
153 group->on_inode_group_list = 0;
154 if (group->on_vfsmount_group_list)
155 list_del_rcu(&group->vfsmount_group_list);
156 group->on_vfsmount_group_list = 0;
160 * Called when a group is no longer interested in getting events. This can be
161 * used if a group is misbehaving or if for some reason a group should no longer
162 * get any filesystem events.
164 void fsnotify_evict_group(struct fsnotify_group *group)
166 mutex_lock(&fsnotify_grp_mutex);
167 __fsnotify_evict_group(group);
168 mutex_unlock(&fsnotify_grp_mutex);
172 * Drop a reference to a group. Free it if it's through.
174 void fsnotify_put_group(struct fsnotify_group *group)
176 if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
180 * OK, now we know that there's no other users *and* we hold mutex,
181 * so no new references will appear
183 __fsnotify_evict_group(group);
185 mutex_unlock(&fsnotify_grp_mutex);
187 fsnotify_destroy_group(group);
191 * Create a new fsnotify_group and hold a reference for the group returned.
193 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
195 struct fsnotify_group *group;
197 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
199 return ERR_PTR(-ENOMEM);
201 /* set to 0 when there a no external references to this group */
202 atomic_set(&group->refcnt, 1);
204 * hits 0 when there are no external references AND no marks for
207 atomic_set(&group->num_marks, 1);
209 mutex_init(&group->notification_mutex);
210 INIT_LIST_HEAD(&group->notification_list);
211 init_waitqueue_head(&group->notification_waitq);
212 group->max_events = UINT_MAX;
214 INIT_LIST_HEAD(&group->inode_group_list);
215 INIT_LIST_HEAD(&group->vfsmount_group_list);
217 spin_lock_init(&group->mark_lock);
218 INIT_LIST_HEAD(&group->marks_list);