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 *entry;
79 spin_lock(&group->mark_lock);
80 list_for_each_entry(entry, &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 mutex_lock(&fsnotify_grp_mutex);
94 if (!group->on_vfsmount_group_list)
95 list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
96 group->on_vfsmount_group_list = 1;
98 mutex_unlock(&fsnotify_grp_mutex);
101 void fsnotify_add_inode_group(struct fsnotify_group *group)
103 mutex_lock(&fsnotify_grp_mutex);
105 if (!group->on_inode_group_list)
106 list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
107 group->on_inode_group_list = 1;
109 mutex_unlock(&fsnotify_grp_mutex);
113 * Final freeing of a group
115 void fsnotify_final_destroy_group(struct fsnotify_group *group)
117 /* clear the notification queue of all events */
118 fsnotify_flush_notify(group);
120 if (group->ops->free_group_priv)
121 group->ops->free_group_priv(group);
127 * Trying to get rid of a group. We need to first get rid of any outstanding
128 * allocations and then free the group. Remember that fsnotify_clear_marks_by_group
129 * could miss marks that are being freed by inode and those marks could still
130 * hold a reference to this group (via group->num_marks) If we get into that
131 * situtation, the fsnotify_final_destroy_group will get called when that final
134 static void fsnotify_destroy_group(struct fsnotify_group *group)
136 /* clear all inode marks for this group */
137 fsnotify_clear_marks_by_group(group);
139 /* past the point of no return, matches the initial value of 1 */
140 if (atomic_dec_and_test(&group->num_marks))
141 fsnotify_final_destroy_group(group);
145 * Remove this group from the global list of groups that will get events
146 * this can be done even if there are still references and things still using
147 * this group. This just stops the group from getting new events.
149 static void __fsnotify_evict_group(struct fsnotify_group *group)
151 BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
153 if (group->on_inode_group_list)
154 list_del_rcu(&group->inode_group_list);
155 group->on_inode_group_list = 0;
156 if (group->on_vfsmount_group_list)
157 list_del_rcu(&group->vfsmount_group_list);
158 group->on_vfsmount_group_list = 0;
162 * Called when a group is no longer interested in getting events. This can be
163 * used if a group is misbehaving or if for some reason a group should no longer
164 * get any filesystem events.
166 void fsnotify_evict_group(struct fsnotify_group *group)
168 mutex_lock(&fsnotify_grp_mutex);
169 __fsnotify_evict_group(group);
170 mutex_unlock(&fsnotify_grp_mutex);
174 * Drop a reference to a group. Free it if it's through.
176 void fsnotify_put_group(struct fsnotify_group *group)
178 if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
182 * OK, now we know that there's no other users *and* we hold mutex,
183 * so no new references will appear
185 __fsnotify_evict_group(group);
188 * now it's off the list, so the only thing we might care about is
191 mutex_unlock(&fsnotify_grp_mutex);
192 synchronize_srcu(&fsnotify_grp_srcu);
194 /* and now it is really dead. _Nothing_ could be seeing it */
195 fsnotify_recalc_global_mask();
196 fsnotify_destroy_group(group);
200 * Create a new fsnotify_group and hold a reference for the group returned.
202 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
204 struct fsnotify_group *group;
206 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
208 return ERR_PTR(-ENOMEM);
210 /* set to 0 when there a no external references to this group */
211 atomic_set(&group->refcnt, 1);
213 * hits 0 when there are no external references AND no marks for
216 atomic_set(&group->num_marks, 1);
218 mutex_init(&group->notification_mutex);
219 INIT_LIST_HEAD(&group->notification_list);
220 init_waitqueue_head(&group->notification_waitq);
221 group->max_events = UINT_MAX;
223 INIT_LIST_HEAD(&group->inode_group_list);
224 INIT_LIST_HEAD(&group->vfsmount_group_list);
226 spin_lock_init(&group->mark_lock);
227 INIT_LIST_HEAD(&group->marks_list);