]>
Commit | Line | Data |
---|---|---|
90586523 EP |
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 <asm/atomic.h> | |
30 | ||
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 filesystem notifications */ | |
36 | LIST_HEAD(fsnotify_groups); | |
37 | /* bitwise OR of all events (FS_*) interesting to some group on this system */ | |
38 | __u32 fsnotify_mask; | |
39 | ||
40 | /* | |
41 | * When a new group registers or changes it's set of interesting events | |
42 | * this function updates the fsnotify_mask to contain all interesting events | |
43 | */ | |
44 | void fsnotify_recalc_global_mask(void) | |
45 | { | |
46 | struct fsnotify_group *group; | |
47 | __u32 mask = 0; | |
48 | int idx; | |
49 | ||
50 | idx = srcu_read_lock(&fsnotify_grp_srcu); | |
51 | list_for_each_entry_rcu(group, &fsnotify_groups, group_list) | |
52 | mask |= group->mask; | |
53 | srcu_read_unlock(&fsnotify_grp_srcu, idx); | |
54 | fsnotify_mask = mask; | |
55 | } | |
56 | ||
3be25f49 EP |
57 | /* |
58 | * Update the group->mask by running all of the marks associated with this | |
59 | * group and finding the bitwise | of all of the mark->mask. If we change | |
60 | * the group->mask we need to update the global mask of events interesting | |
61 | * to the system. | |
62 | */ | |
63 | void fsnotify_recalc_group_mask(struct fsnotify_group *group) | |
64 | { | |
65 | __u32 mask = 0; | |
66 | __u32 old_mask = group->mask; | |
67 | struct fsnotify_mark_entry *entry; | |
68 | ||
69 | spin_lock(&group->mark_lock); | |
70 | list_for_each_entry(entry, &group->mark_entries, g_list) | |
71 | mask |= entry->mask; | |
72 | spin_unlock(&group->mark_lock); | |
73 | ||
74 | group->mask = mask; | |
75 | ||
76 | if (old_mask != mask) | |
77 | fsnotify_recalc_global_mask(); | |
78 | } | |
79 | ||
90586523 EP |
80 | /* |
81 | * Final freeing of a group | |
82 | */ | |
3be25f49 | 83 | void fsnotify_final_destroy_group(struct fsnotify_group *group) |
90586523 | 84 | { |
a2d8bc6c EP |
85 | /* clear the notification queue of all events */ |
86 | fsnotify_flush_notify(group); | |
87 | ||
90586523 EP |
88 | if (group->ops->free_group_priv) |
89 | group->ops->free_group_priv(group); | |
90 | ||
91 | kfree(group); | |
92 | } | |
93 | ||
3be25f49 EP |
94 | /* |
95 | * Trying to get rid of a group. We need to first get rid of any outstanding | |
96 | * allocations and then free the group. Remember that fsnotify_clear_marks_by_group | |
97 | * could miss marks that are being freed by inode and those marks could still | |
98 | * hold a reference to this group (via group->num_marks) If we get into that | |
99 | * situtation, the fsnotify_final_destroy_group will get called when that final | |
100 | * mark is freed. | |
101 | */ | |
102 | static void fsnotify_destroy_group(struct fsnotify_group *group) | |
103 | { | |
104 | /* clear all inode mark entries for this group */ | |
105 | fsnotify_clear_marks_by_group(group); | |
106 | ||
107 | /* past the point of no return, matches the initial value of 1 */ | |
108 | if (atomic_dec_and_test(&group->num_marks)) | |
109 | fsnotify_final_destroy_group(group); | |
110 | } | |
111 | ||
90586523 EP |
112 | /* |
113 | * Remove this group from the global list of groups that will get events | |
114 | * this can be done even if there are still references and things still using | |
115 | * this group. This just stops the group from getting new events. | |
116 | */ | |
117 | static void __fsnotify_evict_group(struct fsnotify_group *group) | |
118 | { | |
119 | BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex)); | |
120 | ||
121 | if (group->on_group_list) | |
122 | list_del_rcu(&group->group_list); | |
123 | group->on_group_list = 0; | |
124 | } | |
125 | ||
126 | /* | |
127 | * Called when a group is no longer interested in getting events. This can be | |
128 | * used if a group is misbehaving or if for some reason a group should no longer | |
129 | * get any filesystem events. | |
130 | */ | |
131 | void fsnotify_evict_group(struct fsnotify_group *group) | |
132 | { | |
133 | mutex_lock(&fsnotify_grp_mutex); | |
134 | __fsnotify_evict_group(group); | |
135 | mutex_unlock(&fsnotify_grp_mutex); | |
136 | } | |
137 | ||
138 | /* | |
139 | * Drop a reference to a group. Free it if it's through. | |
140 | */ | |
141 | void fsnotify_put_group(struct fsnotify_group *group) | |
142 | { | |
143 | if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex)) | |
144 | return; | |
145 | ||
146 | /* | |
147 | * OK, now we know that there's no other users *and* we hold mutex, | |
148 | * so no new references will appear | |
149 | */ | |
150 | __fsnotify_evict_group(group); | |
151 | ||
152 | /* | |
153 | * now it's off the list, so the only thing we might care about is | |
154 | * srcu access.... | |
155 | */ | |
156 | mutex_unlock(&fsnotify_grp_mutex); | |
157 | synchronize_srcu(&fsnotify_grp_srcu); | |
158 | ||
159 | /* and now it is really dead. _Nothing_ could be seeing it */ | |
160 | fsnotify_recalc_global_mask(); | |
161 | fsnotify_destroy_group(group); | |
162 | } | |
163 | ||
90586523 EP |
164 | /* |
165 | * Either finds an existing group which matches the group_num, mask, and ops or | |
166 | * creates a new group and adds it to the global group list. In either case we | |
167 | * take a reference for the group returned. | |
168 | */ | |
74be0cc8 | 169 | struct fsnotify_group *fsnotify_obtain_group(__u32 mask, |
90586523 EP |
170 | const struct fsnotify_ops *ops) |
171 | { | |
74be0cc8 | 172 | struct fsnotify_group *group; |
90586523 EP |
173 | |
174 | /* very low use, simpler locking if we just always alloc */ | |
f0553af0 | 175 | group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); |
90586523 EP |
176 | if (!group) |
177 | return ERR_PTR(-ENOMEM); | |
178 | ||
179 | atomic_set(&group->refcnt, 1); | |
180 | ||
181 | group->on_group_list = 0; | |
90586523 EP |
182 | group->mask = mask; |
183 | ||
a2d8bc6c EP |
184 | mutex_init(&group->notification_mutex); |
185 | INIT_LIST_HEAD(&group->notification_list); | |
186 | init_waitqueue_head(&group->notification_waitq); | |
187 | group->q_len = 0; | |
188 | group->max_events = UINT_MAX; | |
189 | ||
3be25f49 EP |
190 | spin_lock_init(&group->mark_lock); |
191 | atomic_set(&group->num_marks, 0); | |
192 | INIT_LIST_HEAD(&group->mark_entries); | |
193 | ||
90586523 EP |
194 | group->ops = ops; |
195 | ||
196 | mutex_lock(&fsnotify_grp_mutex); | |
90586523 EP |
197 | |
198 | /* group not found, add a new one */ | |
199 | list_add_rcu(&group->group_list, &fsnotify_groups); | |
200 | group->on_group_list = 1; | |
3be25f49 EP |
201 | /* being on the fsnotify_groups list holds one num_marks */ |
202 | atomic_inc(&group->num_marks); | |
90586523 EP |
203 | |
204 | mutex_unlock(&fsnotify_grp_mutex); | |
205 | ||
206 | if (mask) | |
207 | fsnotify_recalc_global_mask(); | |
208 | ||
209 | return group; | |
210 | } |