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);
37 /* bitwise OR of all events (FS_*) interesting to some group on this system */
38 __u32 fsnotify_inode_mask;
39 /* bitwise OR of all events (FS_*) interesting to some group on this system */
40 __u32 fsnotify_vfsmount_mask;
43 * When a new group registers or changes it's set of interesting events
44 * this function updates the fsnotify_mask to contain all interesting events
46 void fsnotify_recalc_global_mask(void)
48 struct fsnotify_group *group;
50 __u32 vfsmount_mask = 0;
52 mutex_lock(&fsnotify_grp_mutex);
53 list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list)
54 inode_mask |= group->mask;
55 list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list)
56 vfsmount_mask |= group->mask;
58 fsnotify_inode_mask = inode_mask;
59 fsnotify_vfsmount_mask = vfsmount_mask;
61 mutex_unlock(&fsnotify_grp_mutex);
65 * Update the group->mask by running all of the marks associated with this
66 * group and finding the bitwise | of all of the mark->mask. If we change
67 * the group->mask we need to update the global mask of events interesting
70 void fsnotify_recalc_group_mask(struct fsnotify_group *group)
73 __u32 old_mask = group->mask;
74 struct fsnotify_mark *mark;
76 spin_lock(&group->mark_lock);
77 list_for_each_entry(mark, &group->marks_list, g_list)
79 spin_unlock(&group->mark_lock);
84 fsnotify_recalc_global_mask();
87 void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
89 struct fsnotify_group *group_iter;
91 mutex_lock(&fsnotify_grp_mutex);
93 if (!group->on_vfsmount_group_list) {
94 list_for_each_entry(group_iter, &fsnotify_vfsmount_groups,
95 vfsmount_group_list) {
96 /* insert in front of this one? */
97 if (group < group_iter) {
98 /* list_add_tail() insert in front of group_iter */
99 list_add_tail_rcu(&group->inode_group_list,
100 &group_iter->inode_group_list);
105 /* apparently we need to be the last entry */
106 list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
109 group->on_vfsmount_group_list = 1;
111 mutex_unlock(&fsnotify_grp_mutex);
114 void fsnotify_add_inode_group(struct fsnotify_group *group)
116 struct fsnotify_group *group_iter;
118 mutex_lock(&fsnotify_grp_mutex);
120 /* add to global group list */
121 if (!group->on_inode_group_list) {
122 list_for_each_entry(group_iter, &fsnotify_inode_groups,
124 if (group < group_iter) {
125 /* list_add_tail() insert in front of group_iter */
126 list_add_tail_rcu(&group->inode_group_list,
127 &group_iter->inode_group_list);
132 /* apparently we need to be the last entry */
133 list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
136 group->on_inode_group_list = 1;
138 mutex_unlock(&fsnotify_grp_mutex);
142 * Final freeing of a group
144 void fsnotify_final_destroy_group(struct fsnotify_group *group)
146 /* clear the notification queue of all events */
147 fsnotify_flush_notify(group);
149 if (group->ops->free_group_priv)
150 group->ops->free_group_priv(group);
156 * Trying to get rid of a group. We need to first get rid of any outstanding
157 * allocations and then free the group. Remember that fsnotify_clear_marks_by_group
158 * could miss marks that are being freed by inode and those marks could still
159 * hold a reference to this group (via group->num_marks) If we get into that
160 * situtation, the fsnotify_final_destroy_group will get called when that final
163 static void fsnotify_destroy_group(struct fsnotify_group *group)
165 /* clear all inode marks for this group */
166 fsnotify_clear_marks_by_group(group);
168 synchronize_srcu(&fsnotify_mark_srcu);
170 /* past the point of no return, matches the initial value of 1 */
171 if (atomic_dec_and_test(&group->num_marks))
172 fsnotify_final_destroy_group(group);
176 * Remove this group from the global list of groups that will get events
177 * this can be done even if there are still references and things still using
178 * this group. This just stops the group from getting new events.
180 static void __fsnotify_evict_group(struct fsnotify_group *group)
182 BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
184 if (group->on_inode_group_list)
185 list_del_rcu(&group->inode_group_list);
186 group->on_inode_group_list = 0;
187 if (group->on_vfsmount_group_list)
188 list_del_rcu(&group->vfsmount_group_list);
189 group->on_vfsmount_group_list = 0;
193 * Called when a group is no longer interested in getting events. This can be
194 * used if a group is misbehaving or if for some reason a group should no longer
195 * get any filesystem events.
197 void fsnotify_evict_group(struct fsnotify_group *group)
199 mutex_lock(&fsnotify_grp_mutex);
200 __fsnotify_evict_group(group);
201 mutex_unlock(&fsnotify_grp_mutex);
205 * Drop a reference to a group. Free it if it's through.
207 void fsnotify_put_group(struct fsnotify_group *group)
209 if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
213 * OK, now we know that there's no other users *and* we hold mutex,
214 * so no new references will appear
216 __fsnotify_evict_group(group);
218 mutex_unlock(&fsnotify_grp_mutex);
220 /* and now it is really dead. _Nothing_ could be seeing it */
221 fsnotify_recalc_global_mask();
222 fsnotify_destroy_group(group);
226 * Create a new fsnotify_group and hold a reference for the group returned.
228 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
230 struct fsnotify_group *group;
232 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
234 return ERR_PTR(-ENOMEM);
236 /* set to 0 when there a no external references to this group */
237 atomic_set(&group->refcnt, 1);
239 * hits 0 when there are no external references AND no marks for
242 atomic_set(&group->num_marks, 1);
244 mutex_init(&group->notification_mutex);
245 INIT_LIST_HEAD(&group->notification_list);
246 init_waitqueue_head(&group->notification_waitq);
247 group->max_events = UINT_MAX;
249 INIT_LIST_HEAD(&group->inode_group_list);
250 INIT_LIST_HEAD(&group->vfsmount_group_list);
252 spin_lock_init(&group->mark_lock);
253 INIT_LIST_HEAD(&group->marks_list);