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 /* protects reads while running the fsnotify_groups list */
34 struct srcu_struct fsnotify_grp_srcu;
35 /* all groups registered to receive inode filesystem notifications */
36 LIST_HEAD(fsnotify_inode_groups);
37 /* all groups registered to receive mount point filesystem notifications */
38 LIST_HEAD(fsnotify_vfsmount_groups);
39 /* bitwise OR of all events (FS_*) interesting to some group on this system */
40 __u32 fsnotify_inode_mask;
41 /* bitwise OR of all events (FS_*) interesting to some group on this system */
42 __u32 fsnotify_vfsmount_mask;
45 * When a new group registers or changes it's set of interesting events
46 * this function updates the fsnotify_mask to contain all interesting events
48 void fsnotify_recalc_global_mask(void)
50 struct fsnotify_group *group;
52 __u32 vfsmount_mask = 0;
55 idx = srcu_read_lock(&fsnotify_grp_srcu);
56 list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list)
57 inode_mask |= group->mask;
58 list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list)
59 vfsmount_mask |= group->mask;
61 srcu_read_unlock(&fsnotify_grp_srcu, idx);
63 fsnotify_inode_mask = inode_mask;
64 fsnotify_vfsmount_mask = vfsmount_mask;
68 * Update the group->mask by running all of the marks associated with this
69 * group and finding the bitwise | of all of the mark->mask. If we change
70 * the group->mask we need to update the global mask of events interesting
73 void fsnotify_recalc_group_mask(struct fsnotify_group *group)
76 __u32 old_mask = group->mask;
77 struct fsnotify_mark *mark;
79 spin_lock(&group->mark_lock);
80 list_for_each_entry(mark, &group->marks_list, g_list)
82 spin_unlock(&group->mark_lock);
87 fsnotify_recalc_global_mask();
90 void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
92 struct fsnotify_group *group_iter;
93 unsigned int priority = group->priority;
95 mutex_lock(&fsnotify_grp_mutex);
97 if (!group->on_vfsmount_group_list) {
98 list_for_each_entry(group_iter, &fsnotify_vfsmount_groups,
99 vfsmount_group_list) {
100 /* insert in front of this one? */
101 if (priority < group_iter->priority) {
102 /* list_add_tail() insert in front of group_iter */
103 list_add_tail_rcu(&group->inode_group_list,
104 &group_iter->inode_group_list);
109 /* apparently we need to be the last entry */
110 list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
113 group->on_vfsmount_group_list = 1;
115 mutex_unlock(&fsnotify_grp_mutex);
118 void fsnotify_add_inode_group(struct fsnotify_group *group)
120 struct fsnotify_group *group_iter;
121 unsigned int priority = group->priority;
123 mutex_lock(&fsnotify_grp_mutex);
125 /* add to global group list, priority 0 first, UINT_MAX last */
126 if (!group->on_inode_group_list) {
127 list_for_each_entry(group_iter, &fsnotify_inode_groups,
129 if (priority < group_iter->priority) {
130 /* list_add_tail() insert in front of group_iter */
131 list_add_tail_rcu(&group->inode_group_list,
132 &group_iter->inode_group_list);
137 /* apparently we need to be the last entry */
138 list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
141 group->on_inode_group_list = 1;
143 mutex_unlock(&fsnotify_grp_mutex);
147 * Final freeing of a group
149 void fsnotify_final_destroy_group(struct fsnotify_group *group)
151 /* clear the notification queue of all events */
152 fsnotify_flush_notify(group);
154 if (group->ops->free_group_priv)
155 group->ops->free_group_priv(group);
161 * Trying to get rid of a group. We need to first get rid of any outstanding
162 * allocations and then free the group. Remember that fsnotify_clear_marks_by_group
163 * could miss marks that are being freed by inode and those marks could still
164 * hold a reference to this group (via group->num_marks) If we get into that
165 * situtation, the fsnotify_final_destroy_group will get called when that final
168 static void fsnotify_destroy_group(struct fsnotify_group *group)
170 /* clear all inode marks for this group */
171 fsnotify_clear_marks_by_group(group);
173 /* past the point of no return, matches the initial value of 1 */
174 if (atomic_dec_and_test(&group->num_marks))
175 fsnotify_final_destroy_group(group);
179 * Remove this group from the global list of groups that will get events
180 * this can be done even if there are still references and things still using
181 * this group. This just stops the group from getting new events.
183 static void __fsnotify_evict_group(struct fsnotify_group *group)
185 BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
187 if (group->on_inode_group_list)
188 list_del_rcu(&group->inode_group_list);
189 group->on_inode_group_list = 0;
190 if (group->on_vfsmount_group_list)
191 list_del_rcu(&group->vfsmount_group_list);
192 group->on_vfsmount_group_list = 0;
196 * Called when a group is no longer interested in getting events. This can be
197 * used if a group is misbehaving or if for some reason a group should no longer
198 * get any filesystem events.
200 void fsnotify_evict_group(struct fsnotify_group *group)
202 mutex_lock(&fsnotify_grp_mutex);
203 __fsnotify_evict_group(group);
204 mutex_unlock(&fsnotify_grp_mutex);
208 * Drop a reference to a group. Free it if it's through.
210 void fsnotify_put_group(struct fsnotify_group *group)
212 if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
216 * OK, now we know that there's no other users *and* we hold mutex,
217 * so no new references will appear
219 __fsnotify_evict_group(group);
222 * now it's off the list, so the only thing we might care about is
225 mutex_unlock(&fsnotify_grp_mutex);
226 synchronize_srcu(&fsnotify_grp_srcu);
228 /* and now it is really dead. _Nothing_ could be seeing it */
229 fsnotify_recalc_global_mask();
230 fsnotify_destroy_group(group);
234 * Create a new fsnotify_group and hold a reference for the group returned.
236 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
238 struct fsnotify_group *group;
240 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
242 return ERR_PTR(-ENOMEM);
244 /* set to 0 when there a no external references to this group */
245 atomic_set(&group->refcnt, 1);
247 * hits 0 when there are no external references AND no marks for
250 atomic_set(&group->num_marks, 1);
252 mutex_init(&group->notification_mutex);
253 INIT_LIST_HEAD(&group->notification_list);
254 init_waitqueue_head(&group->notification_waitq);
255 group->max_events = UINT_MAX;
257 INIT_LIST_HEAD(&group->inode_group_list);
258 INIT_LIST_HEAD(&group->vfsmount_group_list);
260 spin_lock_init(&group->mark_lock);
261 INIT_LIST_HEAD(&group->marks_list);
263 group->priority = UINT_MAX;