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 mask of events relevant to a given inode locked.
35 */
fsnotify_recalc_inode_mask_locked(struct inode * inode)36 static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
37 {
38 struct fsnotify_mark *mark;
39 __u32 new_mask = 0;
40
41 assert_spin_locked(&inode->i_lock);
42
43 hlist_for_each_entry(mark, &inode->i_fsnotify_marks, i.i_list)
44 new_mask |= mark->mask;
45 inode->i_fsnotify_mask = new_mask;
46 }
47
48 /*
49 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
50 * any notifier is interested in hearing for this inode.
51 */
fsnotify_recalc_inode_mask(struct inode * inode)52 void fsnotify_recalc_inode_mask(struct inode *inode)
53 {
54 spin_lock(&inode->i_lock);
55 fsnotify_recalc_inode_mask_locked(inode);
56 spin_unlock(&inode->i_lock);
57
58 __fsnotify_update_child_dentry_flags(inode);
59 }
60
fsnotify_destroy_inode_mark(struct fsnotify_mark * mark)61 void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
62 {
63 struct inode *inode = mark->i.inode;
64
65 BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
66 assert_spin_locked(&mark->lock);
67
68 spin_lock(&inode->i_lock);
69
70 hlist_del_init_rcu(&mark->i.i_list);
71 mark->i.inode = NULL;
72
73 /*
74 * this mark is now off the inode->i_fsnotify_marks list and we
75 * hold the inode->i_lock, so this is the perfect time to update the
76 * inode->i_fsnotify_mask
77 */
78 fsnotify_recalc_inode_mask_locked(inode);
79
80 spin_unlock(&inode->i_lock);
81 }
82
83 /*
84 * Given an inode, destroy all of the marks associated with that inode.
85 */
fsnotify_clear_marks_by_inode(struct inode * inode)86 void fsnotify_clear_marks_by_inode(struct inode *inode)
87 {
88 struct fsnotify_mark *mark, *lmark;
89 struct hlist_node *n;
90 LIST_HEAD(free_list);
91
92 spin_lock(&inode->i_lock);
93 hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, i.i_list) {
94 list_add(&mark->i.free_i_list, &free_list);
95 hlist_del_init_rcu(&mark->i.i_list);
96 fsnotify_get_mark(mark);
97 }
98 spin_unlock(&inode->i_lock);
99
100 list_for_each_entry_safe(mark, lmark, &free_list, i.free_i_list) {
101 struct fsnotify_group *group;
102
103 spin_lock(&mark->lock);
104 fsnotify_get_group(mark->group);
105 group = mark->group;
106 spin_unlock(&mark->lock);
107
108 fsnotify_destroy_mark(mark, group);
109 fsnotify_put_mark(mark);
110 fsnotify_put_group(group);
111 }
112 }
113
114 /*
115 * Given a group clear all of the inode marks associated with that group.
116 */
fsnotify_clear_inode_marks_by_group(struct fsnotify_group * group)117 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
118 {
119 fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
120 }
121
122 /*
123 * given a group and inode, find the mark associated with that combination.
124 * if found take a reference to that mark and return it, else return NULL
125 */
fsnotify_find_inode_mark_locked(struct fsnotify_group * group,struct inode * inode)126 static struct fsnotify_mark *fsnotify_find_inode_mark_locked(
127 struct fsnotify_group *group,
128 struct inode *inode)
129 {
130 struct fsnotify_mark *mark;
131
132 assert_spin_locked(&inode->i_lock);
133
134 hlist_for_each_entry(mark, &inode->i_fsnotify_marks, i.i_list) {
135 if (mark->group == group) {
136 fsnotify_get_mark(mark);
137 return mark;
138 }
139 }
140 return NULL;
141 }
142
143 /*
144 * given a group and inode, find the mark associated with that combination.
145 * if found take a reference to that mark and return it, else return NULL
146 */
fsnotify_find_inode_mark(struct fsnotify_group * group,struct inode * inode)147 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
148 struct inode *inode)
149 {
150 struct fsnotify_mark *mark;
151
152 spin_lock(&inode->i_lock);
153 mark = fsnotify_find_inode_mark_locked(group, inode);
154 spin_unlock(&inode->i_lock);
155
156 return mark;
157 }
158
159 /*
160 * If we are setting a mark mask on an inode mark we should pin the inode
161 * in memory.
162 */
fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark * mark,__u32 mask)163 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
164 __u32 mask)
165 {
166 struct inode *inode;
167
168 assert_spin_locked(&mark->lock);
169
170 if (mask &&
171 mark->i.inode &&
172 !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
173 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
174 inode = igrab(mark->i.inode);
175 /*
176 * we shouldn't be able to get here if the inode wasn't
177 * already safely held in memory. But bug in case it
178 * ever is wrong.
179 */
180 BUG_ON(!inode);
181 }
182 }
183
184 /*
185 * Attach an initialized mark to a given inode.
186 * These marks may be used for the fsnotify backend to determine which
187 * event types should be delivered to which group and for which inodes. These
188 * marks are ordered according to priority, highest number first, and then by
189 * the group's location in memory.
190 */
fsnotify_add_inode_mark(struct fsnotify_mark * mark,struct fsnotify_group * group,struct inode * inode,int allow_dups)191 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
192 struct fsnotify_group *group, struct inode *inode,
193 int allow_dups)
194 {
195 struct fsnotify_mark *lmark, *last = NULL;
196 int ret = 0;
197
198 mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
199
200 BUG_ON(!mutex_is_locked(&group->mark_mutex));
201 assert_spin_locked(&mark->lock);
202
203 spin_lock(&inode->i_lock);
204
205 mark->i.inode = inode;
206
207 /* is mark the first mark? */
208 if (hlist_empty(&inode->i_fsnotify_marks)) {
209 hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
210 goto out;
211 }
212
213 /* should mark be in the middle of the current list? */
214 hlist_for_each_entry(lmark, &inode->i_fsnotify_marks, i.i_list) {
215 last = lmark;
216
217 if ((lmark->group == group) && !allow_dups) {
218 ret = -EEXIST;
219 goto out;
220 }
221
222 if (mark->group->priority < lmark->group->priority)
223 continue;
224
225 if ((mark->group->priority == lmark->group->priority) &&
226 (mark->group < lmark->group))
227 continue;
228
229 hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
230 goto out;
231 }
232
233 BUG_ON(last == NULL);
234 /* mark should be the last entry. last is the current last entry */
235 hlist_add_after_rcu(&last->i.i_list, &mark->i.i_list);
236 out:
237 fsnotify_recalc_inode_mask_locked(inode);
238 spin_unlock(&inode->i_lock);
239
240 return ret;
241 }
242
243 /**
244 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
245 * @list: list of inodes being unmounted (sb->s_inodes)
246 *
247 * Called during unmount with no locks held, so needs to be safe against
248 * concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
249 */
fsnotify_unmount_inodes(struct list_head * list)250 void fsnotify_unmount_inodes(struct list_head *list)
251 {
252 struct inode *inode, *next_i, *need_iput = NULL;
253
254 spin_lock(&inode_sb_list_lock);
255 list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
256 struct inode *need_iput_tmp;
257
258 /*
259 * We cannot __iget() an inode in state I_FREEING,
260 * I_WILL_FREE, or I_NEW which is fine because by that point
261 * the inode cannot have any associated watches.
262 */
263 spin_lock(&inode->i_lock);
264 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
265 spin_unlock(&inode->i_lock);
266 continue;
267 }
268
269 /*
270 * If i_count is zero, the inode cannot have any watches and
271 * doing an __iget/iput with MS_ACTIVE clear would actually
272 * evict all inodes with zero i_count from icache which is
273 * unnecessarily violent and may in fact be illegal to do.
274 */
275 if (!atomic_read(&inode->i_count)) {
276 spin_unlock(&inode->i_lock);
277 continue;
278 }
279
280 need_iput_tmp = need_iput;
281 need_iput = NULL;
282
283 /* In case fsnotify_inode_delete() drops a reference. */
284 if (inode != need_iput_tmp)
285 __iget(inode);
286 else
287 need_iput_tmp = NULL;
288 spin_unlock(&inode->i_lock);
289
290 /* In case the dropping of a reference would nuke next_i. */
291 if ((&next_i->i_sb_list != list) &&
292 atomic_read(&next_i->i_count)) {
293 spin_lock(&next_i->i_lock);
294 if (!(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
295 __iget(next_i);
296 need_iput = next_i;
297 }
298 spin_unlock(&next_i->i_lock);
299 }
300
301 /*
302 * We can safely drop inode_sb_list_lock here because we hold
303 * references on both inode and next_i. Also no new inodes
304 * will be added since the umount has begun.
305 */
306 spin_unlock(&inode_sb_list_lock);
307
308 if (need_iput_tmp)
309 iput(need_iput_tmp);
310
311 /* for each watch, send FS_UNMOUNT and then remove it */
312 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
313
314 fsnotify_inode_delete(inode);
315
316 iput(inode);
317
318 spin_lock(&inode_sb_list_lock);
319 }
320 spin_unlock(&inode_sb_list_lock);
321 }
322