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/fs.h>
20 #include <linux/init.h>
21 #include <linux/kernel.h>
22 #include <linux/module.h>
23 #include <linux/mutex.h>
24 #include <linux/spinlock.h>
25
26 #include <linux/atomic.h>
27
28 #include <linux/fsnotify_backend.h>
29 #include "fsnotify.h"
30
31 #include "../internal.h"
32
33 /*
34 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
35 * any notifier is interested in hearing for this inode.
36 */
fsnotify_recalc_inode_mask(struct inode * inode)37 void fsnotify_recalc_inode_mask(struct inode *inode)
38 {
39 spin_lock(&inode->i_lock);
40 inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
41 spin_unlock(&inode->i_lock);
42
43 __fsnotify_update_child_dentry_flags(inode);
44 }
45
fsnotify_destroy_inode_mark(struct fsnotify_mark * mark)46 void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
47 {
48 struct inode *inode = mark->inode;
49
50 BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
51 assert_spin_locked(&mark->lock);
52
53 spin_lock(&inode->i_lock);
54
55 hlist_del_init_rcu(&mark->obj_list);
56 mark->inode = NULL;
57
58 /*
59 * this mark is now off the inode->i_fsnotify_marks list and we
60 * hold the inode->i_lock, so this is the perfect time to update the
61 * inode->i_fsnotify_mask
62 */
63 inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
64 spin_unlock(&inode->i_lock);
65 }
66
67 /*
68 * Given an inode, destroy all of the marks associated with that inode.
69 */
fsnotify_clear_marks_by_inode(struct inode * inode)70 void fsnotify_clear_marks_by_inode(struct inode *inode)
71 {
72 struct fsnotify_mark *mark;
73 struct hlist_node *n;
74 LIST_HEAD(free_list);
75
76 spin_lock(&inode->i_lock);
77 hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, obj_list) {
78 list_add(&mark->free_list, &free_list);
79 hlist_del_init_rcu(&mark->obj_list);
80 fsnotify_get_mark(mark);
81 }
82 spin_unlock(&inode->i_lock);
83
84 fsnotify_destroy_marks(&free_list);
85 }
86
87 /*
88 * Given a group clear all of the inode marks associated with that group.
89 */
fsnotify_clear_inode_marks_by_group(struct fsnotify_group * group)90 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
91 {
92 fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
93 }
94
95 /*
96 * given a group and inode, find the mark associated with that combination.
97 * if found take a reference to that mark and return it, else return NULL
98 */
fsnotify_find_inode_mark(struct fsnotify_group * group,struct inode * inode)99 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
100 struct inode *inode)
101 {
102 struct fsnotify_mark *mark;
103
104 spin_lock(&inode->i_lock);
105 mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
106 spin_unlock(&inode->i_lock);
107
108 return mark;
109 }
110
111 /*
112 * If we are setting a mark mask on an inode mark we should pin the inode
113 * in memory.
114 */
fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark * mark,__u32 mask)115 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
116 __u32 mask)
117 {
118 struct inode *inode;
119
120 assert_spin_locked(&mark->lock);
121
122 if (mask &&
123 mark->inode &&
124 !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
125 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
126 inode = igrab(mark->inode);
127 /*
128 * we shouldn't be able to get here if the inode wasn't
129 * already safely held in memory. But bug in case it
130 * ever is wrong.
131 */
132 BUG_ON(!inode);
133 }
134 }
135
136 /*
137 * Attach an initialized mark to a given inode.
138 * These marks may be used for the fsnotify backend to determine which
139 * event types should be delivered to which group and for which inodes. These
140 * marks are ordered according to priority, highest number first, and then by
141 * the group's location in memory.
142 */
fsnotify_add_inode_mark(struct fsnotify_mark * mark,struct fsnotify_group * group,struct inode * inode,int allow_dups)143 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
144 struct fsnotify_group *group, struct inode *inode,
145 int allow_dups)
146 {
147 int ret;
148
149 mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
150
151 BUG_ON(!mutex_is_locked(&group->mark_mutex));
152 assert_spin_locked(&mark->lock);
153
154 spin_lock(&inode->i_lock);
155 mark->inode = inode;
156 ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
157 allow_dups);
158 inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
159 spin_unlock(&inode->i_lock);
160
161 return ret;
162 }
163
164 /**
165 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
166 * @list: list of inodes being unmounted (sb->s_inodes)
167 *
168 * Called during unmount with no locks held, so needs to be safe against
169 * concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
170 */
fsnotify_unmount_inodes(struct list_head * list)171 void fsnotify_unmount_inodes(struct list_head *list)
172 {
173 struct inode *inode, *next_i, *need_iput = NULL;
174
175 spin_lock(&inode_sb_list_lock);
176 list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
177 struct inode *need_iput_tmp;
178
179 /*
180 * We cannot __iget() an inode in state I_FREEING,
181 * I_WILL_FREE, or I_NEW which is fine because by that point
182 * the inode cannot have any associated watches.
183 */
184 spin_lock(&inode->i_lock);
185 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
186 spin_unlock(&inode->i_lock);
187 continue;
188 }
189
190 /*
191 * If i_count is zero, the inode cannot have any watches and
192 * doing an __iget/iput with MS_ACTIVE clear would actually
193 * evict all inodes with zero i_count from icache which is
194 * unnecessarily violent and may in fact be illegal to do.
195 */
196 if (!atomic_read(&inode->i_count)) {
197 spin_unlock(&inode->i_lock);
198 continue;
199 }
200
201 need_iput_tmp = need_iput;
202 need_iput = NULL;
203
204 /* In case fsnotify_inode_delete() drops a reference. */
205 if (inode != need_iput_tmp)
206 __iget(inode);
207 else
208 need_iput_tmp = NULL;
209 spin_unlock(&inode->i_lock);
210
211 /* In case the dropping of a reference would nuke next_i. */
212 while (&next_i->i_sb_list != list) {
213 spin_lock(&next_i->i_lock);
214 if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
215 atomic_read(&next_i->i_count)) {
216 __iget(next_i);
217 need_iput = next_i;
218 spin_unlock(&next_i->i_lock);
219 break;
220 }
221 spin_unlock(&next_i->i_lock);
222 next_i = list_entry(next_i->i_sb_list.next,
223 struct inode, i_sb_list);
224 }
225
226 /*
227 * We can safely drop inode_sb_list_lock here because either
228 * we actually hold references on both inode and next_i or
229 * end of list. Also no new inodes will be added since the
230 * umount has begun.
231 */
232 spin_unlock(&inode_sb_list_lock);
233
234 if (need_iput_tmp)
235 iput(need_iput_tmp);
236
237 /* for each watch, send FS_UNMOUNT and then remove it */
238 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
239
240 fsnotify_inode_delete(inode);
241
242 iput(inode);
243
244 spin_lock(&inode_sb_list_lock);
245 }
246 spin_unlock(&inode_sb_list_lock);
247 }
248