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-rw-r--r--fs/notify/fsnotify.c186
1 files changed, 186 insertions, 0 deletions
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
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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/dcache.h>
20#include <linux/fs.h>
21#include <linux/init.h>
22#include <linux/module.h>
23#include <linux/srcu.h>
24
25#include <linux/fsnotify_backend.h>
26#include "fsnotify.h"
27
28/*
29 * Clear all of the marks on an inode when it is being evicted from core
30 */
31void __fsnotify_inode_delete(struct inode *inode)
32{
33 fsnotify_clear_marks_by_inode(inode);
34}
35EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
36
37/*
38 * Given an inode, first check if we care what happens to our children. Inotify
39 * and dnotify both tell their parents about events. If we care about any event
40 * on a child we run all of our children and set a dentry flag saying that the
41 * parent cares. Thus when an event happens on a child it can quickly tell if
42 * if there is a need to find a parent and send the event to the parent.
43 */
44void __fsnotify_update_child_dentry_flags(struct inode *inode)
45{
46 struct dentry *alias;
47 int watched;
48
49 if (!S_ISDIR(inode->i_mode))
50 return;
51
52 /* determine if the children should tell inode about their events */
53 watched = fsnotify_inode_watches_children(inode);
54
55 spin_lock(&dcache_lock);
56 /* run all of the dentries associated with this inode. Since this is a
57 * directory, there damn well better only be one item on this list */
58 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
59 struct dentry *child;
60
61 /* run all of the children of the original inode and fix their
62 * d_flags to indicate parental interest (their parent is the
63 * original inode) */
64 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
65 if (!child->d_inode)
66 continue;
67
68 spin_lock(&child->d_lock);
69 if (watched)
70 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
71 else
72 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
73 spin_unlock(&child->d_lock);
74 }
75 }
76 spin_unlock(&dcache_lock);
77}
78
79/* Notify this dentry's parent about a child's events. */
80void __fsnotify_parent(struct dentry *dentry, __u32 mask)
81{
82 struct dentry *parent;
83 struct inode *p_inode;
84 bool send = false;
85 bool should_update_children = false;
86
87 if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
88 return;
89
90 spin_lock(&dentry->d_lock);
91 parent = dentry->d_parent;
92 p_inode = parent->d_inode;
93
94 if (fsnotify_inode_watches_children(p_inode)) {
95 if (p_inode->i_fsnotify_mask & mask) {
96 dget(parent);
97 send = true;
98 }
99 } else {
100 /*
101 * The parent doesn't care about events on it's children but
102 * at least one child thought it did. We need to run all the
103 * children and update their d_flags to let them know p_inode
104 * doesn't care about them any more.
105 */
106 dget(parent);
107 should_update_children = true;
108 }
109
110 spin_unlock(&dentry->d_lock);
111
112 if (send) {
113 /* we are notifying a parent so come up with the new mask which
114 * specifies these are events which came from a child. */
115 mask |= FS_EVENT_ON_CHILD;
116
117 fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
118 dentry->d_name.name, 0);
119 dput(parent);
120 }
121
122 if (unlikely(should_update_children)) {
123 __fsnotify_update_child_dentry_flags(p_inode);
124 dput(parent);
125 }
126}
127EXPORT_SYMBOL_GPL(__fsnotify_parent);
128
129/*
130 * This is the main call to fsnotify. The VFS calls into hook specific functions
131 * in linux/fsnotify.h. Those functions then in turn call here. Here will call
132 * out to all of the registered fsnotify_group. Those groups can then use the
133 * notification event in whatever means they feel necessary.
134 */
135void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, const char *file_name, u32 cookie)
136{
137 struct fsnotify_group *group;
138 struct fsnotify_event *event = NULL;
139 int idx;
140 /* global tests shouldn't care about events on child only the specific event */
141 __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
142
143 if (list_empty(&fsnotify_groups))
144 return;
145
146 if (!(test_mask & fsnotify_mask))
147 return;
148
149 if (!(test_mask & to_tell->i_fsnotify_mask))
150 return;
151 /*
152 * SRCU!! the groups list is very very much read only and the path is
153 * very hot. The VAST majority of events are not going to need to do
154 * anything other than walk the list so it's crazy to pre-allocate.
155 */
156 idx = srcu_read_lock(&fsnotify_grp_srcu);
157 list_for_each_entry_rcu(group, &fsnotify_groups, group_list) {
158 if (test_mask & group->mask) {
159 if (!group->ops->should_send_event(group, to_tell, mask))
160 continue;
161 if (!event) {
162 event = fsnotify_create_event(to_tell, mask, data, data_is, file_name, cookie);
163 /* shit, we OOM'd and now we can't tell, maybe
164 * someday someone else will want to do something
165 * here */
166 if (!event)
167 break;
168 }
169 group->ops->handle_event(group, event);
170 }
171 }
172 srcu_read_unlock(&fsnotify_grp_srcu, idx);
173 /*
174 * fsnotify_create_event() took a reference so the event can't be cleaned
175 * up while we are still trying to add it to lists, drop that one.
176 */
177 if (event)
178 fsnotify_put_event(event);
179}
180EXPORT_SYMBOL_GPL(fsnotify);
181
182static __init int fsnotify_init(void)
183{
184 return init_srcu_struct(&fsnotify_grp_srcu);
185}
186subsys_initcall(fsnotify_init);
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