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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/*
20 * fsnotify inode mark locking/lifetime/and refcnting
21 *
22 * REFCNT:
23 * The group->recnt and mark->refcnt tell how many "things" in the kernel
24 * currently are referencing the objects. Both kind of objects typically will
25 * live inside the kernel with a refcnt of 2, one for its creation and one for
26 * the reference a group and a mark hold to each other.
27 * If you are holding the appropriate locks, you can take a reference and the
28 * object itself is guaranteed to survive until the reference is dropped.
29 *
30 * LOCKING:
31 * There are 3 locks involved with fsnotify inode marks and they MUST be taken
32 * in order as follows:
33 *
34 * group->mark_mutex
35 * mark->lock
36 * inode->i_lock
37 *
38 * group->mark_mutex protects the marks_list anchored inside a given group and
39 * each mark is hooked via the g_list. It also protects the groups private
40 * data (i.e group limits).
41
42 * mark->lock protects the marks attributes like its masks and flags.
43 * Furthermore it protects the access to a reference of the group that the mark
44 * is assigned to as well as the access to a reference of the inode/vfsmount
45 * that is being watched by the mark.
46 *
47 * inode->i_lock protects the i_fsnotify_marks list anchored inside a
48 * given inode and each mark is hooked via the i_list. (and sorta the
49 * free_i_list)
50 *
51 *
52 * LIFETIME:
53 * Inode marks survive between when they are added to an inode and when their
54 * refcnt==0.
55 *
56 * The inode mark can be cleared for a number of different reasons including:
57 * - The inode is unlinked for the last time. (fsnotify_inode_remove)
58 * - The inode is being evicted from cache. (fsnotify_inode_delete)
59 * - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
60 * - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
61 * - The fsnotify_group associated with the mark is going away and all such marks
62 * need to be cleaned up. (fsnotify_clear_marks_by_group)
63 *
64 * Worst case we are given an inode and need to clean up all the marks on that
65 * inode. We take i_lock and walk the i_fsnotify_marks safely. For each
66 * mark on the list we take a reference (so the mark can't disappear under us).
67 * We remove that mark form the inode's list of marks and we add this mark to a
68 * private list anchored on the stack using i_free_list; we walk i_free_list
69 * and before we destroy the mark we make sure that we dont race with a
70 * concurrent destroy_group by getting a ref to the marks group and taking the
71 * groups mutex.
72
73 * Very similarly for freeing by group, except we use free_g_list.
74 *
75 * This has the very interesting property of being able to run concurrently with
76 * any (or all) other directions.
77 */
78
79#include <linux/fs.h>
80#include <linux/init.h>
81#include <linux/kernel.h>
82#include <linux/kthread.h>
83#include <linux/module.h>
84#include <linux/mutex.h>
85#include <linux/slab.h>
86#include <linux/spinlock.h>
87#include <linux/srcu.h>
88
89#include <linux/atomic.h>
90
91#include <linux/fsnotify_backend.h>
92#include "fsnotify.h"
93
94struct srcu_struct fsnotify_mark_srcu;
95static DEFINE_SPINLOCK(destroy_lock);
96static LIST_HEAD(destroy_list);
97static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
98
99void fsnotify_get_mark(struct fsnotify_mark *mark)
100{
101 atomic_inc(&mark->refcnt);
102}
103
104void fsnotify_put_mark(struct fsnotify_mark *mark)
105{
106 if (atomic_dec_and_test(&mark->refcnt)) {
107 if (mark->group)
108 fsnotify_put_group(mark->group);
109 mark->free_mark(mark);
110 }
111}
112
113/*
114 * Any time a mark is getting freed we end up here.
115 * The caller had better be holding a reference to this mark so we don't actually
116 * do the final put under the mark->lock
117 */
118void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
119 struct fsnotify_group *group)
120{
121 struct inode *inode = NULL;
122
123 BUG_ON(!mutex_is_locked(&group->mark_mutex));
124
125 spin_lock(&mark->lock);
126
127 /* something else already called this function on this mark */
128 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
129 spin_unlock(&mark->lock);
130 return;
131 }
132
133 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
134
135 if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
136 inode = mark->i.inode;
137 fsnotify_destroy_inode_mark(mark);
138 } else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
139 fsnotify_destroy_vfsmount_mark(mark);
140 else
141 BUG();
142
143 list_del_init(&mark->g_list);
144
145 spin_unlock(&mark->lock);
146
147 if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
148 iput(inode);
149 /* release lock temporarily */
150 mutex_unlock(&group->mark_mutex);
151
152 spin_lock(&destroy_lock);
153 list_add(&mark->destroy_list, &destroy_list);
154 spin_unlock(&destroy_lock);
155 wake_up(&destroy_waitq);
156 /*
157 * We don't necessarily have a ref on mark from caller so the above destroy
158 * may have actually freed it, unless this group provides a 'freeing_mark'
159 * function which must be holding a reference.
160 */
161
162 /*
163 * Some groups like to know that marks are being freed. This is a
164 * callback to the group function to let it know that this mark
165 * is being freed.
166 */
167 if (group->ops->freeing_mark)
168 group->ops->freeing_mark(mark, group);
169
170 /*
171 * __fsnotify_update_child_dentry_flags(inode);
172 *
173 * I really want to call that, but we can't, we have no idea if the inode
174 * still exists the second we drop the mark->lock.
175 *
176 * The next time an event arrive to this inode from one of it's children
177 * __fsnotify_parent will see that the inode doesn't care about it's
178 * children and will update all of these flags then. So really this
179 * is just a lazy update (and could be a perf win...)
180 */
181
182 atomic_dec(&group->num_marks);
183
184 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
185}
186
187void fsnotify_destroy_mark(struct fsnotify_mark *mark,
188 struct fsnotify_group *group)
189{
190 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
191 fsnotify_destroy_mark_locked(mark, group);
192 mutex_unlock(&group->mark_mutex);
193}
194
195void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
196{
197 assert_spin_locked(&mark->lock);
198
199 mark->mask = mask;
200
201 if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
202 fsnotify_set_inode_mark_mask_locked(mark, mask);
203}
204
205void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
206{
207 assert_spin_locked(&mark->lock);
208
209 mark->ignored_mask = mask;
210}
211
212/*
213 * Attach an initialized mark to a given group and fs object.
214 * These marks may be used for the fsnotify backend to determine which
215 * event types should be delivered to which group.
216 */
217int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
218 struct fsnotify_group *group, struct inode *inode,
219 struct vfsmount *mnt, int allow_dups)
220{
221 int ret = 0;
222
223 BUG_ON(inode && mnt);
224 BUG_ON(!inode && !mnt);
225 BUG_ON(!mutex_is_locked(&group->mark_mutex));
226
227 /*
228 * LOCKING ORDER!!!!
229 * group->mark_mutex
230 * mark->lock
231 * inode->i_lock
232 */
233 spin_lock(&mark->lock);
234 mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
235
236 fsnotify_get_group(group);
237 mark->group = group;
238 list_add(&mark->g_list, &group->marks_list);
239 atomic_inc(&group->num_marks);
240 fsnotify_get_mark(mark); /* for i_list and g_list */
241
242 if (inode) {
243 ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
244 if (ret)
245 goto err;
246 } else if (mnt) {
247 ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups);
248 if (ret)
249 goto err;
250 } else {
251 BUG();
252 }
253
254 /* this will pin the object if appropriate */
255 fsnotify_set_mark_mask_locked(mark, mark->mask);
256 spin_unlock(&mark->lock);
257
258 if (inode)
259 __fsnotify_update_child_dentry_flags(inode);
260
261 return ret;
262err:
263 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
264 list_del_init(&mark->g_list);
265 fsnotify_put_group(group);
266 mark->group = NULL;
267 atomic_dec(&group->num_marks);
268
269 spin_unlock(&mark->lock);
270
271 spin_lock(&destroy_lock);
272 list_add(&mark->destroy_list, &destroy_list);
273 spin_unlock(&destroy_lock);
274 wake_up(&destroy_waitq);
275
276 return ret;
277}
278
279int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
280 struct inode *inode, struct vfsmount *mnt, int allow_dups)
281{
282 int ret;
283 mutex_lock(&group->mark_mutex);
284 ret = fsnotify_add_mark_locked(mark, group, inode, mnt, allow_dups);
285 mutex_unlock(&group->mark_mutex);
286 return ret;
287}
288
289/*
290 * clear any marks in a group in which mark->flags & flags is true
291 */
292void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
293 unsigned int flags)
294{
295 struct fsnotify_mark *lmark, *mark;
296
297 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
298 list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
299 if (mark->flags & flags) {
300 fsnotify_get_mark(mark);
301 fsnotify_destroy_mark_locked(mark, group);
302 fsnotify_put_mark(mark);
303 }
304 }
305 mutex_unlock(&group->mark_mutex);
306}
307
308/*
309 * Given a group, destroy all of the marks associated with that group.
310 */
311void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
312{
313 fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1);
314}
315
316void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
317{
318 assert_spin_locked(&old->lock);
319 new->i.inode = old->i.inode;
320 new->m.mnt = old->m.mnt;
321 if (old->group)
322 fsnotify_get_group(old->group);
323 new->group = old->group;
324 new->mask = old->mask;
325 new->free_mark = old->free_mark;
326}
327
328/*
329 * Nothing fancy, just initialize lists and locks and counters.
330 */
331void fsnotify_init_mark(struct fsnotify_mark *mark,
332 void (*free_mark)(struct fsnotify_mark *mark))
333{
334 memset(mark, 0, sizeof(*mark));
335 spin_lock_init(&mark->lock);
336 atomic_set(&mark->refcnt, 1);
337 mark->free_mark = free_mark;
338}
339
340static int fsnotify_mark_destroy(void *ignored)
341{
342 struct fsnotify_mark *mark, *next;
343 LIST_HEAD(private_destroy_list);
344
345 for (;;) {
346 spin_lock(&destroy_lock);
347 /* exchange the list head */
348 list_replace_init(&destroy_list, &private_destroy_list);
349 spin_unlock(&destroy_lock);
350
351 synchronize_srcu(&fsnotify_mark_srcu);
352
353 list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
354 list_del_init(&mark->destroy_list);
355 fsnotify_put_mark(mark);
356 }
357
358 wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
359 }
360
361 return 0;
362}
363
364static int __init fsnotify_mark_init(void)
365{
366 struct task_struct *thread;
367
368 thread = kthread_run(fsnotify_mark_destroy, NULL,
369 "fsnotify_mark");
370 if (IS_ERR(thread))
371 panic("unable to start fsnotify mark destruction thread.");
372
373 return 0;
374}
375device_initcall(fsnotify_mark_init);
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/*
20 * fsnotify inode mark locking/lifetime/and refcnting
21 *
22 * REFCNT:
23 * The mark->refcnt tells how many "things" in the kernel currently are
24 * referencing this object. The object typically will live inside the kernel
25 * with a refcnt of 2, one for each list it is on (i_list, g_list). Any task
26 * which can find this object holding the appropriete locks, can take a reference
27 * and the object itself is guaranteed to survive until the reference is dropped.
28 *
29 * LOCKING:
30 * There are 3 spinlocks involved with fsnotify inode marks and they MUST
31 * be taken in order as follows:
32 *
33 * mark->lock
34 * group->mark_lock
35 * inode->i_lock
36 *
37 * mark->lock protects 2 things, mark->group and mark->inode. You must hold
38 * that lock to dereference either of these things (they could be NULL even with
39 * the lock)
40 *
41 * group->mark_lock protects the marks_list anchored inside a given group
42 * and each mark is hooked via the g_list. It also sorta protects the
43 * free_g_list, which when used is anchored by a private list on the stack of the
44 * task which held the group->mark_lock.
45 *
46 * inode->i_lock protects the i_fsnotify_marks list anchored inside a
47 * given inode and each mark is hooked via the i_list. (and sorta the
48 * free_i_list)
49 *
50 *
51 * LIFETIME:
52 * Inode marks survive between when they are added to an inode and when their
53 * refcnt==0.
54 *
55 * The inode mark can be cleared for a number of different reasons including:
56 * - The inode is unlinked for the last time. (fsnotify_inode_remove)
57 * - The inode is being evicted from cache. (fsnotify_inode_delete)
58 * - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
59 * - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
60 * - The fsnotify_group associated with the mark is going away and all such marks
61 * need to be cleaned up. (fsnotify_clear_marks_by_group)
62 *
63 * Worst case we are given an inode and need to clean up all the marks on that
64 * inode. We take i_lock and walk the i_fsnotify_marks safely. For each
65 * mark on the list we take a reference (so the mark can't disappear under us).
66 * We remove that mark form the inode's list of marks and we add this mark to a
67 * private list anchored on the stack using i_free_list; At this point we no
68 * longer fear anything finding the mark using the inode's list of marks.
69 *
70 * We can safely and locklessly run the private list on the stack of everything
71 * we just unattached from the original inode. For each mark on the private list
72 * we grab the mark-> and can thus dereference mark->group and mark->inode. If
73 * we see the group and inode are not NULL we take those locks. Now holding all
74 * 3 locks we can completely remove the mark from other tasks finding it in the
75 * future. Remember, 10 things might already be referencing this mark, but they
76 * better be holding a ref. We drop our reference we took before we unhooked it
77 * from the inode. When the ref hits 0 we can free the mark.
78 *
79 * Very similarly for freeing by group, except we use free_g_list.
80 *
81 * This has the very interesting property of being able to run concurrently with
82 * any (or all) other directions.
83 */
84
85#include <linux/fs.h>
86#include <linux/init.h>
87#include <linux/kernel.h>
88#include <linux/kthread.h>
89#include <linux/module.h>
90#include <linux/mutex.h>
91#include <linux/slab.h>
92#include <linux/spinlock.h>
93#include <linux/srcu.h>
94
95#include <linux/atomic.h>
96
97#include <linux/fsnotify_backend.h>
98#include "fsnotify.h"
99
100struct srcu_struct fsnotify_mark_srcu;
101static DEFINE_SPINLOCK(destroy_lock);
102static LIST_HEAD(destroy_list);
103static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
104
105void fsnotify_get_mark(struct fsnotify_mark *mark)
106{
107 atomic_inc(&mark->refcnt);
108}
109
110void fsnotify_put_mark(struct fsnotify_mark *mark)
111{
112 if (atomic_dec_and_test(&mark->refcnt))
113 mark->free_mark(mark);
114}
115
116/*
117 * Any time a mark is getting freed we end up here.
118 * The caller had better be holding a reference to this mark so we don't actually
119 * do the final put under the mark->lock
120 */
121void fsnotify_destroy_mark(struct fsnotify_mark *mark)
122{
123 struct fsnotify_group *group;
124 struct inode *inode = NULL;
125
126 spin_lock(&mark->lock);
127
128 group = mark->group;
129
130 /* something else already called this function on this mark */
131 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
132 spin_unlock(&mark->lock);
133 return;
134 }
135
136 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
137
138 spin_lock(&group->mark_lock);
139
140 if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
141 inode = mark->i.inode;
142 fsnotify_destroy_inode_mark(mark);
143 } else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
144 fsnotify_destroy_vfsmount_mark(mark);
145 else
146 BUG();
147
148 list_del_init(&mark->g_list);
149
150 spin_unlock(&group->mark_lock);
151 spin_unlock(&mark->lock);
152
153 spin_lock(&destroy_lock);
154 list_add(&mark->destroy_list, &destroy_list);
155 spin_unlock(&destroy_lock);
156 wake_up(&destroy_waitq);
157
158 /*
159 * Some groups like to know that marks are being freed. This is a
160 * callback to the group function to let it know that this mark
161 * is being freed.
162 */
163 if (group->ops->freeing_mark)
164 group->ops->freeing_mark(mark, group);
165
166 /*
167 * __fsnotify_update_child_dentry_flags(inode);
168 *
169 * I really want to call that, but we can't, we have no idea if the inode
170 * still exists the second we drop the mark->lock.
171 *
172 * The next time an event arrive to this inode from one of it's children
173 * __fsnotify_parent will see that the inode doesn't care about it's
174 * children and will update all of these flags then. So really this
175 * is just a lazy update (and could be a perf win...)
176 */
177
178 if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
179 iput(inode);
180
181 /*
182 * We don't necessarily have a ref on mark from caller so the above iput
183 * may have already destroyed it. Don't touch from now on.
184 */
185
186 /*
187 * it's possible that this group tried to destroy itself, but this
188 * this mark was simultaneously being freed by inode. If that's the
189 * case, we finish freeing the group here.
190 */
191 if (unlikely(atomic_dec_and_test(&group->num_marks)))
192 fsnotify_final_destroy_group(group);
193}
194
195void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
196{
197 assert_spin_locked(&mark->lock);
198
199 mark->mask = mask;
200
201 if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
202 fsnotify_set_inode_mark_mask_locked(mark, mask);
203}
204
205void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
206{
207 assert_spin_locked(&mark->lock);
208
209 mark->ignored_mask = mask;
210}
211
212/*
213 * Attach an initialized mark to a given group and fs object.
214 * These marks may be used for the fsnotify backend to determine which
215 * event types should be delivered to which group.
216 */
217int fsnotify_add_mark(struct fsnotify_mark *mark,
218 struct fsnotify_group *group, struct inode *inode,
219 struct vfsmount *mnt, int allow_dups)
220{
221 int ret = 0;
222
223 BUG_ON(inode && mnt);
224 BUG_ON(!inode && !mnt);
225
226 /*
227 * LOCKING ORDER!!!!
228 * mark->lock
229 * group->mark_lock
230 * inode->i_lock
231 */
232 spin_lock(&mark->lock);
233 spin_lock(&group->mark_lock);
234
235 mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
236
237 mark->group = group;
238 list_add(&mark->g_list, &group->marks_list);
239 atomic_inc(&group->num_marks);
240 fsnotify_get_mark(mark); /* for i_list and g_list */
241
242 if (inode) {
243 ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
244 if (ret)
245 goto err;
246 } else if (mnt) {
247 ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups);
248 if (ret)
249 goto err;
250 } else {
251 BUG();
252 }
253
254 spin_unlock(&group->mark_lock);
255
256 /* this will pin the object if appropriate */
257 fsnotify_set_mark_mask_locked(mark, mark->mask);
258
259 spin_unlock(&mark->lock);
260
261 if (inode)
262 __fsnotify_update_child_dentry_flags(inode);
263
264 return ret;
265err:
266 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
267 list_del_init(&mark->g_list);
268 mark->group = NULL;
269 atomic_dec(&group->num_marks);
270
271 spin_unlock(&group->mark_lock);
272 spin_unlock(&mark->lock);
273
274 spin_lock(&destroy_lock);
275 list_add(&mark->destroy_list, &destroy_list);
276 spin_unlock(&destroy_lock);
277 wake_up(&destroy_waitq);
278
279 return ret;
280}
281
282/*
283 * clear any marks in a group in which mark->flags & flags is true
284 */
285void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
286 unsigned int flags)
287{
288 struct fsnotify_mark *lmark, *mark;
289 LIST_HEAD(free_list);
290
291 spin_lock(&group->mark_lock);
292 list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
293 if (mark->flags & flags) {
294 list_add(&mark->free_g_list, &free_list);
295 list_del_init(&mark->g_list);
296 fsnotify_get_mark(mark);
297 }
298 }
299 spin_unlock(&group->mark_lock);
300
301 list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
302 fsnotify_destroy_mark(mark);
303 fsnotify_put_mark(mark);
304 }
305}
306
307/*
308 * Given a group, destroy all of the marks associated with that group.
309 */
310void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
311{
312 fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1);
313}
314
315void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
316{
317 assert_spin_locked(&old->lock);
318 new->i.inode = old->i.inode;
319 new->m.mnt = old->m.mnt;
320 new->group = old->group;
321 new->mask = old->mask;
322 new->free_mark = old->free_mark;
323}
324
325/*
326 * Nothing fancy, just initialize lists and locks and counters.
327 */
328void fsnotify_init_mark(struct fsnotify_mark *mark,
329 void (*free_mark)(struct fsnotify_mark *mark))
330{
331 memset(mark, 0, sizeof(*mark));
332 spin_lock_init(&mark->lock);
333 atomic_set(&mark->refcnt, 1);
334 mark->free_mark = free_mark;
335}
336
337static int fsnotify_mark_destroy(void *ignored)
338{
339 struct fsnotify_mark *mark, *next;
340 LIST_HEAD(private_destroy_list);
341
342 for (;;) {
343 spin_lock(&destroy_lock);
344 /* exchange the list head */
345 list_replace_init(&destroy_list, &private_destroy_list);
346 spin_unlock(&destroy_lock);
347
348 synchronize_srcu(&fsnotify_mark_srcu);
349
350 list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
351 list_del_init(&mark->destroy_list);
352 fsnotify_put_mark(mark);
353 }
354
355 wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
356 }
357
358 return 0;
359}
360
361static int __init fsnotify_mark_init(void)
362{
363 struct task_struct *thread;
364
365 thread = kthread_run(fsnotify_mark_destroy, NULL,
366 "fsnotify_mark");
367 if (IS_ERR(thread))
368 panic("unable to start fsnotify mark destruction thread.");
369
370 return 0;
371}
372device_initcall(fsnotify_mark_init);