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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; | |
7131485a | 35 | /* all groups registered to receive inode filesystem notifications */ |
19c2a0e1 | 36 | LIST_HEAD(fsnotify_inode_groups); |
7131485a EP |
37 | /* all groups registered to receive mount point filesystem notifications */ |
38 | LIST_HEAD(fsnotify_vfsmount_groups); | |
90586523 | 39 | /* bitwise OR of all events (FS_*) interesting to some group on this system */ |
19c2a0e1 | 40 | __u32 fsnotify_inode_mask; |
7131485a EP |
41 | /* bitwise OR of all events (FS_*) interesting to some group on this system */ |
42 | __u32 fsnotify_vfsmount_mask; | |
90586523 EP |
43 | |
44 | /* | |
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 | |
47 | */ | |
48 | void fsnotify_recalc_global_mask(void) | |
49 | { | |
50 | struct fsnotify_group *group; | |
7131485a EP |
51 | __u32 inode_mask = 0; |
52 | __u32 vfsmount_mask = 0; | |
90586523 EP |
53 | int idx; |
54 | ||
55 | idx = srcu_read_lock(&fsnotify_grp_srcu); | |
19c2a0e1 | 56 | list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) |
7131485a EP |
57 | inode_mask |= group->mask; |
58 | list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) | |
59 | vfsmount_mask |= group->mask; | |
60 | ||
90586523 | 61 | srcu_read_unlock(&fsnotify_grp_srcu, idx); |
7131485a EP |
62 | |
63 | fsnotify_inode_mask = inode_mask; | |
64 | fsnotify_vfsmount_mask = vfsmount_mask; | |
90586523 EP |
65 | } |
66 | ||
3be25f49 EP |
67 | /* |
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 | |
71 | * to the system. | |
72 | */ | |
73 | void fsnotify_recalc_group_mask(struct fsnotify_group *group) | |
74 | { | |
75 | __u32 mask = 0; | |
76 | __u32 old_mask = group->mask; | |
841bdc10 | 77 | struct fsnotify_mark *mark; |
3be25f49 EP |
78 | |
79 | spin_lock(&group->mark_lock); | |
841bdc10 EP |
80 | list_for_each_entry(mark, &group->marks_list, g_list) |
81 | mask |= mark->mask; | |
3be25f49 EP |
82 | spin_unlock(&group->mark_lock); |
83 | ||
84 | group->mask = mask; | |
85 | ||
86 | if (old_mask != mask) | |
87 | fsnotify_recalc_global_mask(); | |
88 | } | |
89 | ||
7131485a EP |
90 | void fsnotify_add_vfsmount_group(struct fsnotify_group *group) |
91 | { | |
cb2d429f | 92 | struct fsnotify_group *group_iter; |
cb2d429f | 93 | |
7131485a EP |
94 | mutex_lock(&fsnotify_grp_mutex); |
95 | ||
cb2d429f EP |
96 | if (!group->on_vfsmount_group_list) { |
97 | list_for_each_entry(group_iter, &fsnotify_vfsmount_groups, | |
98 | vfsmount_group_list) { | |
99 | /* insert in front of this one? */ | |
08ae8938 | 100 | if (group < group_iter) { |
cb2d429f EP |
101 | /* list_add_tail() insert in front of group_iter */ |
102 | list_add_tail_rcu(&group->inode_group_list, | |
103 | &group_iter->inode_group_list); | |
104 | goto out; | |
105 | } | |
106 | } | |
107 | ||
108 | /* apparently we need to be the last entry */ | |
7131485a | 109 | list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups); |
cb2d429f EP |
110 | } |
111 | out: | |
7131485a EP |
112 | group->on_vfsmount_group_list = 1; |
113 | ||
114 | mutex_unlock(&fsnotify_grp_mutex); | |
115 | } | |
116 | ||
4ca76352 | 117 | void fsnotify_add_inode_group(struct fsnotify_group *group) |
19c2a0e1 | 118 | { |
cb2d429f | 119 | struct fsnotify_group *group_iter; |
cb2d429f | 120 | |
4ca76352 | 121 | mutex_lock(&fsnotify_grp_mutex); |
19c2a0e1 | 122 | |
08ae8938 | 123 | /* add to global group list */ |
cb2d429f EP |
124 | if (!group->on_inode_group_list) { |
125 | list_for_each_entry(group_iter, &fsnotify_inode_groups, | |
126 | inode_group_list) { | |
08ae8938 | 127 | if (group < group_iter) { |
cb2d429f EP |
128 | /* list_add_tail() insert in front of group_iter */ |
129 | list_add_tail_rcu(&group->inode_group_list, | |
130 | &group_iter->inode_group_list); | |
131 | goto out; | |
132 | } | |
133 | } | |
134 | ||
135 | /* apparently we need to be the last entry */ | |
4ca76352 | 136 | list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups); |
cb2d429f EP |
137 | } |
138 | out: | |
19c2a0e1 | 139 | group->on_inode_group_list = 1; |
4ca76352 EP |
140 | |
141 | mutex_unlock(&fsnotify_grp_mutex); | |
19c2a0e1 EP |
142 | } |
143 | ||
90586523 EP |
144 | /* |
145 | * Final freeing of a group | |
146 | */ | |
3be25f49 | 147 | void fsnotify_final_destroy_group(struct fsnotify_group *group) |
90586523 | 148 | { |
a2d8bc6c EP |
149 | /* clear the notification queue of all events */ |
150 | fsnotify_flush_notify(group); | |
151 | ||
90586523 EP |
152 | if (group->ops->free_group_priv) |
153 | group->ops->free_group_priv(group); | |
154 | ||
155 | kfree(group); | |
156 | } | |
157 | ||
3be25f49 EP |
158 | /* |
159 | * Trying to get rid of a group. We need to first get rid of any outstanding | |
160 | * allocations and then free the group. Remember that fsnotify_clear_marks_by_group | |
161 | * could miss marks that are being freed by inode and those marks could still | |
162 | * hold a reference to this group (via group->num_marks) If we get into that | |
163 | * situtation, the fsnotify_final_destroy_group will get called when that final | |
164 | * mark is freed. | |
165 | */ | |
166 | static void fsnotify_destroy_group(struct fsnotify_group *group) | |
167 | { | |
e61ce867 | 168 | /* clear all inode marks for this group */ |
3be25f49 EP |
169 | fsnotify_clear_marks_by_group(group); |
170 | ||
171 | /* past the point of no return, matches the initial value of 1 */ | |
172 | if (atomic_dec_and_test(&group->num_marks)) | |
173 | fsnotify_final_destroy_group(group); | |
174 | } | |
175 | ||
90586523 EP |
176 | /* |
177 | * Remove this group from the global list of groups that will get events | |
178 | * this can be done even if there are still references and things still using | |
179 | * this group. This just stops the group from getting new events. | |
180 | */ | |
181 | static void __fsnotify_evict_group(struct fsnotify_group *group) | |
182 | { | |
183 | BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex)); | |
184 | ||
19c2a0e1 EP |
185 | if (group->on_inode_group_list) |
186 | list_del_rcu(&group->inode_group_list); | |
187 | group->on_inode_group_list = 0; | |
7131485a EP |
188 | if (group->on_vfsmount_group_list) |
189 | list_del_rcu(&group->vfsmount_group_list); | |
190 | group->on_vfsmount_group_list = 0; | |
90586523 EP |
191 | } |
192 | ||
193 | /* | |
194 | * Called when a group is no longer interested in getting events. This can be | |
195 | * used if a group is misbehaving or if for some reason a group should no longer | |
196 | * get any filesystem events. | |
197 | */ | |
198 | void fsnotify_evict_group(struct fsnotify_group *group) | |
199 | { | |
200 | mutex_lock(&fsnotify_grp_mutex); | |
201 | __fsnotify_evict_group(group); | |
202 | mutex_unlock(&fsnotify_grp_mutex); | |
203 | } | |
204 | ||
205 | /* | |
206 | * Drop a reference to a group. Free it if it's through. | |
207 | */ | |
208 | void fsnotify_put_group(struct fsnotify_group *group) | |
209 | { | |
210 | if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex)) | |
211 | return; | |
212 | ||
213 | /* | |
214 | * OK, now we know that there's no other users *and* we hold mutex, | |
215 | * so no new references will appear | |
216 | */ | |
217 | __fsnotify_evict_group(group); | |
218 | ||
219 | /* | |
220 | * now it's off the list, so the only thing we might care about is | |
221 | * srcu access.... | |
222 | */ | |
223 | mutex_unlock(&fsnotify_grp_mutex); | |
224 | synchronize_srcu(&fsnotify_grp_srcu); | |
225 | ||
226 | /* and now it is really dead. _Nothing_ could be seeing it */ | |
227 | fsnotify_recalc_global_mask(); | |
228 | fsnotify_destroy_group(group); | |
229 | } | |
230 | ||
90586523 | 231 | /* |
ffab8340 | 232 | * Create a new fsnotify_group and hold a reference for the group returned. |
90586523 | 233 | */ |
0d2e2a1d | 234 | struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) |
90586523 | 235 | { |
74be0cc8 | 236 | struct fsnotify_group *group; |
90586523 | 237 | |
f0553af0 | 238 | group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); |
90586523 EP |
239 | if (!group) |
240 | return ERR_PTR(-ENOMEM); | |
241 | ||
36fddeba | 242 | /* set to 0 when there a no external references to this group */ |
90586523 | 243 | atomic_set(&group->refcnt, 1); |
36fddeba EP |
244 | /* |
245 | * hits 0 when there are no external references AND no marks for | |
246 | * this group | |
247 | */ | |
248 | atomic_set(&group->num_marks, 1); | |
249 | ||
a2d8bc6c EP |
250 | mutex_init(&group->notification_mutex); |
251 | INIT_LIST_HEAD(&group->notification_list); | |
252 | init_waitqueue_head(&group->notification_waitq); | |
a2d8bc6c EP |
253 | group->max_events = UINT_MAX; |
254 | ||
4ca76352 | 255 | INIT_LIST_HEAD(&group->inode_group_list); |
7131485a | 256 | INIT_LIST_HEAD(&group->vfsmount_group_list); |
4ca76352 | 257 | |
3be25f49 | 258 | spin_lock_init(&group->mark_lock); |
e61ce867 | 259 | INIT_LIST_HEAD(&group->marks_list); |
3be25f49 | 260 | |
90586523 EP |
261 | group->ops = ops; |
262 | ||
90586523 EP |
263 | return group; |
264 | } |