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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; | |
35 | /* all groups registered to receive filesystem notifications */ | |
19c2a0e1 | 36 | LIST_HEAD(fsnotify_inode_groups); |
90586523 | 37 | /* bitwise OR of all events (FS_*) interesting to some group on this system */ |
19c2a0e1 | 38 | __u32 fsnotify_inode_mask; |
90586523 EP |
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); | |
19c2a0e1 | 51 | list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) |
90586523 EP |
52 | mask |= group->mask; |
53 | srcu_read_unlock(&fsnotify_grp_srcu, idx); | |
19c2a0e1 | 54 | fsnotify_inode_mask = mask; |
90586523 EP |
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 | ||
4ca76352 | 80 | void fsnotify_add_inode_group(struct fsnotify_group *group) |
19c2a0e1 | 81 | { |
4ca76352 | 82 | mutex_lock(&fsnotify_grp_mutex); |
19c2a0e1 | 83 | |
4ca76352 EP |
84 | if (!group->on_inode_group_list) |
85 | list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups); | |
19c2a0e1 | 86 | group->on_inode_group_list = 1; |
4ca76352 EP |
87 | |
88 | mutex_unlock(&fsnotify_grp_mutex); | |
19c2a0e1 EP |
89 | } |
90 | ||
90586523 EP |
91 | /* |
92 | * Final freeing of a group | |
93 | */ | |
3be25f49 | 94 | void fsnotify_final_destroy_group(struct fsnotify_group *group) |
90586523 | 95 | { |
a2d8bc6c EP |
96 | /* clear the notification queue of all events */ |
97 | fsnotify_flush_notify(group); | |
98 | ||
90586523 EP |
99 | if (group->ops->free_group_priv) |
100 | group->ops->free_group_priv(group); | |
101 | ||
102 | kfree(group); | |
103 | } | |
104 | ||
3be25f49 EP |
105 | /* |
106 | * Trying to get rid of a group. We need to first get rid of any outstanding | |
107 | * allocations and then free the group. Remember that fsnotify_clear_marks_by_group | |
108 | * could miss marks that are being freed by inode and those marks could still | |
109 | * hold a reference to this group (via group->num_marks) If we get into that | |
110 | * situtation, the fsnotify_final_destroy_group will get called when that final | |
111 | * mark is freed. | |
112 | */ | |
113 | static void fsnotify_destroy_group(struct fsnotify_group *group) | |
114 | { | |
115 | /* clear all inode mark entries for this group */ | |
116 | fsnotify_clear_marks_by_group(group); | |
117 | ||
118 | /* past the point of no return, matches the initial value of 1 */ | |
119 | if (atomic_dec_and_test(&group->num_marks)) | |
120 | fsnotify_final_destroy_group(group); | |
121 | } | |
122 | ||
90586523 EP |
123 | /* |
124 | * Remove this group from the global list of groups that will get events | |
125 | * this can be done even if there are still references and things still using | |
126 | * this group. This just stops the group from getting new events. | |
127 | */ | |
128 | static void __fsnotify_evict_group(struct fsnotify_group *group) | |
129 | { | |
130 | BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex)); | |
131 | ||
19c2a0e1 EP |
132 | if (group->on_inode_group_list) |
133 | list_del_rcu(&group->inode_group_list); | |
134 | group->on_inode_group_list = 0; | |
90586523 EP |
135 | } |
136 | ||
137 | /* | |
138 | * Called when a group is no longer interested in getting events. This can be | |
139 | * used if a group is misbehaving or if for some reason a group should no longer | |
140 | * get any filesystem events. | |
141 | */ | |
142 | void fsnotify_evict_group(struct fsnotify_group *group) | |
143 | { | |
144 | mutex_lock(&fsnotify_grp_mutex); | |
145 | __fsnotify_evict_group(group); | |
146 | mutex_unlock(&fsnotify_grp_mutex); | |
147 | } | |
148 | ||
149 | /* | |
150 | * Drop a reference to a group. Free it if it's through. | |
151 | */ | |
152 | void fsnotify_put_group(struct fsnotify_group *group) | |
153 | { | |
154 | if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex)) | |
155 | return; | |
156 | ||
157 | /* | |
158 | * OK, now we know that there's no other users *and* we hold mutex, | |
159 | * so no new references will appear | |
160 | */ | |
161 | __fsnotify_evict_group(group); | |
162 | ||
163 | /* | |
164 | * now it's off the list, so the only thing we might care about is | |
165 | * srcu access.... | |
166 | */ | |
167 | mutex_unlock(&fsnotify_grp_mutex); | |
168 | synchronize_srcu(&fsnotify_grp_srcu); | |
169 | ||
170 | /* and now it is really dead. _Nothing_ could be seeing it */ | |
171 | fsnotify_recalc_global_mask(); | |
172 | fsnotify_destroy_group(group); | |
173 | } | |
174 | ||
90586523 | 175 | /* |
ffab8340 | 176 | * Create a new fsnotify_group and hold a reference for the group returned. |
90586523 | 177 | */ |
0d2e2a1d | 178 | struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) |
90586523 | 179 | { |
74be0cc8 | 180 | struct fsnotify_group *group; |
90586523 | 181 | |
f0553af0 | 182 | group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); |
90586523 EP |
183 | if (!group) |
184 | return ERR_PTR(-ENOMEM); | |
185 | ||
36fddeba | 186 | /* set to 0 when there a no external references to this group */ |
90586523 | 187 | atomic_set(&group->refcnt, 1); |
36fddeba EP |
188 | /* |
189 | * hits 0 when there are no external references AND no marks for | |
190 | * this group | |
191 | */ | |
192 | atomic_set(&group->num_marks, 1); | |
193 | ||
a2d8bc6c EP |
194 | mutex_init(&group->notification_mutex); |
195 | INIT_LIST_HEAD(&group->notification_list); | |
196 | init_waitqueue_head(&group->notification_waitq); | |
a2d8bc6c EP |
197 | group->max_events = UINT_MAX; |
198 | ||
4ca76352 EP |
199 | INIT_LIST_HEAD(&group->inode_group_list); |
200 | ||
3be25f49 | 201 | spin_lock_init(&group->mark_lock); |
3be25f49 EP |
202 | INIT_LIST_HEAD(&group->mark_entries); |
203 | ||
90586523 EP |
204 | group->ops = ops; |
205 | ||
90586523 EP |
206 | return group; |
207 | } |