]>
Commit | Line | Data |
---|---|---|
5444e298 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 | /* | |
20 | * fsnotify inode mark locking/lifetime/and refcnting | |
21 | * | |
22 | * REFCNT: | |
9756b918 LS |
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. | |
5444e298 EP |
29 | * |
30 | * LOCKING: | |
9756b918 LS |
31 | * There are 3 locks involved with fsnotify inode marks and they MUST be taken |
32 | * in order as follows: | |
5444e298 | 33 | * |
9756b918 | 34 | * group->mark_mutex |
5444e298 | 35 | * mark->lock |
5444e298 EP |
36 | * inode->i_lock |
37 | * | |
9756b918 LS |
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. | |
5444e298 EP |
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 | |
9756b918 LS |
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 | ||
5444e298 EP |
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> | |
75c1be48 | 82 | #include <linux/kthread.h> |
5444e298 EP |
83 | #include <linux/module.h> |
84 | #include <linux/mutex.h> | |
85 | #include <linux/slab.h> | |
86 | #include <linux/spinlock.h> | |
75c1be48 | 87 | #include <linux/srcu.h> |
5444e298 | 88 | |
60063497 | 89 | #include <linux/atomic.h> |
5444e298 EP |
90 | |
91 | #include <linux/fsnotify_backend.h> | |
92 | #include "fsnotify.h" | |
93 | ||
75c1be48 EP |
94 | struct srcu_struct fsnotify_mark_srcu; |
95 | static DEFINE_SPINLOCK(destroy_lock); | |
96 | static LIST_HEAD(destroy_list); | |
97 | static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq); | |
98 | ||
5444e298 EP |
99 | void fsnotify_get_mark(struct fsnotify_mark *mark) |
100 | { | |
101 | atomic_inc(&mark->refcnt); | |
102 | } | |
103 | ||
104 | void fsnotify_put_mark(struct fsnotify_mark *mark) | |
105 | { | |
23e964c2 LS |
106 | if (atomic_dec_and_test(&mark->refcnt)) { |
107 | if (mark->group) | |
108 | fsnotify_put_group(mark->group); | |
5444e298 | 109 | mark->free_mark(mark); |
23e964c2 | 110 | } |
5444e298 EP |
111 | } |
112 | ||
0809ab69 JK |
113 | /* Calculate mask of events for a list of marks */ |
114 | u32 fsnotify_recalc_mask(struct hlist_head *head) | |
115 | { | |
116 | u32 new_mask = 0; | |
117 | struct fsnotify_mark *mark; | |
118 | ||
119 | hlist_for_each_entry(mark, head, obj_list) | |
120 | new_mask |= mark->mask; | |
121 | return new_mask; | |
122 | } | |
123 | ||
5444e298 EP |
124 | /* |
125 | * Any time a mark is getting freed we end up here. | |
126 | * The caller had better be holding a reference to this mark so we don't actually | |
127 | * do the final put under the mark->lock | |
128 | */ | |
d5a335b8 LS |
129 | void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark, |
130 | struct fsnotify_group *group) | |
5444e298 | 131 | { |
0d48b7f0 | 132 | struct inode *inode = NULL; |
5444e298 | 133 | |
d5a335b8 LS |
134 | BUG_ON(!mutex_is_locked(&group->mark_mutex)); |
135 | ||
104d06f0 | 136 | spin_lock(&mark->lock); |
5444e298 | 137 | |
700307a2 EP |
138 | /* something else already called this function on this mark */ |
139 | if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { | |
5444e298 | 140 | spin_unlock(&mark->lock); |
e2a29943 | 141 | return; |
5444e298 EP |
142 | } |
143 | ||
700307a2 EP |
144 | mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; |
145 | ||
0d48b7f0 | 146 | if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) { |
0809ab69 | 147 | inode = mark->inode; |
b31d397e | 148 | fsnotify_destroy_inode_mark(mark); |
0d48b7f0 EP |
149 | } else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT) |
150 | fsnotify_destroy_vfsmount_mark(mark); | |
5444e298 EP |
151 | else |
152 | BUG(); | |
153 | ||
154 | list_del_init(&mark->g_list); | |
5444e298 | 155 | |
5444e298 | 156 | spin_unlock(&mark->lock); |
d5a335b8 | 157 | |
6960b0d9 LS |
158 | if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) |
159 | iput(inode); | |
d5a335b8 | 160 | /* release lock temporarily */ |
986ab098 | 161 | mutex_unlock(&group->mark_mutex); |
5444e298 | 162 | |
75c1be48 | 163 | spin_lock(&destroy_lock); |
37d469e7 | 164 | list_add(&mark->g_list, &destroy_list); |
75c1be48 EP |
165 | spin_unlock(&destroy_lock); |
166 | wake_up(&destroy_waitq); | |
6960b0d9 LS |
167 | /* |
168 | * We don't necessarily have a ref on mark from caller so the above destroy | |
169 | * may have actually freed it, unless this group provides a 'freeing_mark' | |
170 | * function which must be holding a reference. | |
171 | */ | |
75c1be48 | 172 | |
5444e298 EP |
173 | /* |
174 | * Some groups like to know that marks are being freed. This is a | |
175 | * callback to the group function to let it know that this mark | |
176 | * is being freed. | |
177 | */ | |
178 | if (group->ops->freeing_mark) | |
179 | group->ops->freeing_mark(mark, group); | |
180 | ||
181 | /* | |
182 | * __fsnotify_update_child_dentry_flags(inode); | |
183 | * | |
184 | * I really want to call that, but we can't, we have no idea if the inode | |
185 | * still exists the second we drop the mark->lock. | |
186 | * | |
187 | * The next time an event arrive to this inode from one of it's children | |
188 | * __fsnotify_parent will see that the inode doesn't care about it's | |
189 | * children and will update all of these flags then. So really this | |
190 | * is just a lazy update (and could be a perf win...) | |
191 | */ | |
192 | ||
23e964c2 | 193 | atomic_dec(&group->num_marks); |
d5a335b8 | 194 | |
6960b0d9 | 195 | mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
d5a335b8 LS |
196 | } |
197 | ||
198 | void fsnotify_destroy_mark(struct fsnotify_mark *mark, | |
199 | struct fsnotify_group *group) | |
200 | { | |
6960b0d9 | 201 | mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
d5a335b8 LS |
202 | fsnotify_destroy_mark_locked(mark, group); |
203 | mutex_unlock(&group->mark_mutex); | |
5444e298 EP |
204 | } |
205 | ||
0809ab69 JK |
206 | /* |
207 | * Destroy all marks in the given list. The marks must be already detached from | |
208 | * the original inode / vfsmount. | |
209 | */ | |
210 | void fsnotify_destroy_marks(struct list_head *to_free) | |
211 | { | |
212 | struct fsnotify_mark *mark, *lmark; | |
213 | struct fsnotify_group *group; | |
214 | ||
215 | list_for_each_entry_safe(mark, lmark, to_free, free_list) { | |
216 | spin_lock(&mark->lock); | |
217 | fsnotify_get_group(mark->group); | |
218 | group = mark->group; | |
219 | spin_unlock(&mark->lock); | |
220 | ||
221 | fsnotify_destroy_mark(mark, group); | |
222 | fsnotify_put_mark(mark); | |
223 | fsnotify_put_group(group); | |
224 | } | |
225 | } | |
226 | ||
90b1e7a5 EP |
227 | void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask) |
228 | { | |
229 | assert_spin_locked(&mark->lock); | |
230 | ||
231 | mark->mask = mask; | |
232 | ||
233 | if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) | |
234 | fsnotify_set_inode_mark_mask_locked(mark, mask); | |
235 | } | |
236 | ||
33af5e32 EP |
237 | void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask) |
238 | { | |
239 | assert_spin_locked(&mark->lock); | |
240 | ||
241 | mark->ignored_mask = mask; | |
242 | } | |
90b1e7a5 | 243 | |
8edc6e16 JK |
244 | /* |
245 | * Sorting function for lists of fsnotify marks. | |
246 | * | |
247 | * Fanotify supports different notification classes (reflected as priority of | |
248 | * notification group). Events shall be passed to notification groups in | |
249 | * decreasing priority order. To achieve this marks in notification lists for | |
250 | * inodes and vfsmounts are sorted so that priorities of corresponding groups | |
251 | * are descending. | |
252 | * | |
253 | * Furthermore correct handling of the ignore mask requires processing inode | |
254 | * and vfsmount marks of each group together. Using the group address as | |
255 | * further sort criterion provides a unique sorting order and thus we can | |
256 | * merge inode and vfsmount lists of marks in linear time and find groups | |
257 | * present in both lists. | |
258 | * | |
259 | * A return value of 1 signifies that b has priority over a. | |
260 | * A return value of 0 signifies that the two marks have to be handled together. | |
261 | * A return value of -1 signifies that a has priority over b. | |
262 | */ | |
263 | int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b) | |
264 | { | |
265 | if (a == b) | |
266 | return 0; | |
267 | if (!a) | |
268 | return 1; | |
269 | if (!b) | |
270 | return -1; | |
271 | if (a->priority < b->priority) | |
272 | return 1; | |
273 | if (a->priority > b->priority) | |
274 | return -1; | |
275 | if (a < b) | |
276 | return 1; | |
277 | return -1; | |
278 | } | |
279 | ||
0809ab69 JK |
280 | /* Add mark into proper place in given list of marks */ |
281 | int fsnotify_add_mark_list(struct hlist_head *head, struct fsnotify_mark *mark, | |
282 | int allow_dups) | |
283 | { | |
284 | struct fsnotify_mark *lmark, *last = NULL; | |
285 | int cmp; | |
286 | ||
287 | /* is mark the first mark? */ | |
288 | if (hlist_empty(head)) { | |
289 | hlist_add_head_rcu(&mark->obj_list, head); | |
290 | return 0; | |
291 | } | |
292 | ||
293 | /* should mark be in the middle of the current list? */ | |
294 | hlist_for_each_entry(lmark, head, obj_list) { | |
295 | last = lmark; | |
296 | ||
297 | if ((lmark->group == mark->group) && !allow_dups) | |
298 | return -EEXIST; | |
299 | ||
300 | cmp = fsnotify_compare_groups(lmark->group, mark->group); | |
301 | if (cmp >= 0) { | |
302 | hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list); | |
303 | return 0; | |
304 | } | |
305 | } | |
306 | ||
307 | BUG_ON(last == NULL); | |
308 | /* mark should be the last entry. last is the current last entry */ | |
309 | hlist_add_behind_rcu(&mark->obj_list, &last->obj_list); | |
310 | return 0; | |
311 | } | |
312 | ||
5444e298 EP |
313 | /* |
314 | * Attach an initialized mark to a given group and fs object. | |
315 | * These marks may be used for the fsnotify backend to determine which | |
316 | * event types should be delivered to which group. | |
317 | */ | |
d5a335b8 LS |
318 | int fsnotify_add_mark_locked(struct fsnotify_mark *mark, |
319 | struct fsnotify_group *group, struct inode *inode, | |
320 | struct vfsmount *mnt, int allow_dups) | |
5444e298 EP |
321 | { |
322 | int ret = 0; | |
323 | ||
5444e298 EP |
324 | BUG_ON(inode && mnt); |
325 | BUG_ON(!inode && !mnt); | |
d5a335b8 | 326 | BUG_ON(!mutex_is_locked(&group->mark_mutex)); |
5444e298 | 327 | |
5444e298 EP |
328 | /* |
329 | * LOCKING ORDER!!!! | |
986ab098 | 330 | * group->mark_mutex |
104d06f0 | 331 | * mark->lock |
5444e298 EP |
332 | * inode->i_lock |
333 | */ | |
104d06f0 | 334 | spin_lock(&mark->lock); |
700307a2 EP |
335 | mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE; |
336 | ||
23e964c2 | 337 | fsnotify_get_group(group); |
5444e298 EP |
338 | mark->group = group; |
339 | list_add(&mark->g_list, &group->marks_list); | |
340 | atomic_inc(&group->num_marks); | |
341 | fsnotify_get_mark(mark); /* for i_list and g_list */ | |
342 | ||
343 | if (inode) { | |
344 | ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups); | |
345 | if (ret) | |
346 | goto err; | |
0d48b7f0 EP |
347 | } else if (mnt) { |
348 | ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups); | |
349 | if (ret) | |
350 | goto err; | |
5444e298 EP |
351 | } else { |
352 | BUG(); | |
353 | } | |
354 | ||
90b1e7a5 EP |
355 | /* this will pin the object if appropriate */ |
356 | fsnotify_set_mark_mask_locked(mark, mark->mask); | |
5444e298 EP |
357 | spin_unlock(&mark->lock); |
358 | ||
359 | if (inode) | |
360 | __fsnotify_update_child_dentry_flags(inode); | |
361 | ||
362 | return ret; | |
363 | err: | |
700307a2 | 364 | mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; |
5444e298 | 365 | list_del_init(&mark->g_list); |
23e964c2 | 366 | fsnotify_put_group(group); |
75c1be48 | 367 | mark->group = NULL; |
5444e298 | 368 | atomic_dec(&group->num_marks); |
5444e298 | 369 | |
5444e298 EP |
370 | spin_unlock(&mark->lock); |
371 | ||
75c1be48 | 372 | spin_lock(&destroy_lock); |
37d469e7 | 373 | list_add(&mark->g_list, &destroy_list); |
75c1be48 EP |
374 | spin_unlock(&destroy_lock); |
375 | wake_up(&destroy_waitq); | |
376 | ||
5444e298 EP |
377 | return ret; |
378 | } | |
379 | ||
d5a335b8 LS |
380 | int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group, |
381 | struct inode *inode, struct vfsmount *mnt, int allow_dups) | |
382 | { | |
383 | int ret; | |
384 | mutex_lock(&group->mark_mutex); | |
385 | ret = fsnotify_add_mark_locked(mark, group, inode, mnt, allow_dups); | |
386 | mutex_unlock(&group->mark_mutex); | |
387 | return ret; | |
388 | } | |
389 | ||
0809ab69 JK |
390 | /* |
391 | * Given a list of marks, find the mark associated with given group. If found | |
392 | * take a reference to that mark and return it, else return NULL. | |
393 | */ | |
394 | struct fsnotify_mark *fsnotify_find_mark(struct hlist_head *head, | |
395 | struct fsnotify_group *group) | |
396 | { | |
397 | struct fsnotify_mark *mark; | |
398 | ||
399 | hlist_for_each_entry(mark, head, obj_list) { | |
400 | if (mark->group == group) { | |
401 | fsnotify_get_mark(mark); | |
402 | return mark; | |
403 | } | |
404 | } | |
405 | return NULL; | |
406 | } | |
407 | ||
5444e298 | 408 | /* |
4d92604c | 409 | * clear any marks in a group in which mark->flags & flags is true |
5444e298 | 410 | */ |
4d92604c EP |
411 | void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, |
412 | unsigned int flags) | |
5444e298 EP |
413 | { |
414 | struct fsnotify_mark *lmark, *mark; | |
5444e298 | 415 | |
6960b0d9 | 416 | mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
5444e298 | 417 | list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) { |
4d92604c | 418 | if (mark->flags & flags) { |
4d92604c | 419 | fsnotify_get_mark(mark); |
64c20d2a LS |
420 | fsnotify_destroy_mark_locked(mark, group); |
421 | fsnotify_put_mark(mark); | |
4d92604c | 422 | } |
5444e298 | 423 | } |
986ab098 | 424 | mutex_unlock(&group->mark_mutex); |
5444e298 EP |
425 | } |
426 | ||
4d92604c EP |
427 | /* |
428 | * Given a group, destroy all of the marks associated with that group. | |
429 | */ | |
430 | void fsnotify_clear_marks_by_group(struct fsnotify_group *group) | |
431 | { | |
432 | fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1); | |
433 | } | |
434 | ||
5444e298 EP |
435 | void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old) |
436 | { | |
437 | assert_spin_locked(&old->lock); | |
0809ab69 JK |
438 | new->inode = old->inode; |
439 | new->mnt = old->mnt; | |
23e964c2 LS |
440 | if (old->group) |
441 | fsnotify_get_group(old->group); | |
5444e298 EP |
442 | new->group = old->group; |
443 | new->mask = old->mask; | |
444 | new->free_mark = old->free_mark; | |
445 | } | |
446 | ||
447 | /* | |
448 | * Nothing fancy, just initialize lists and locks and counters. | |
449 | */ | |
450 | void fsnotify_init_mark(struct fsnotify_mark *mark, | |
451 | void (*free_mark)(struct fsnotify_mark *mark)) | |
452 | { | |
ba643f04 | 453 | memset(mark, 0, sizeof(*mark)); |
5444e298 EP |
454 | spin_lock_init(&mark->lock); |
455 | atomic_set(&mark->refcnt, 1); | |
5444e298 EP |
456 | mark->free_mark = free_mark; |
457 | } | |
75c1be48 EP |
458 | |
459 | static int fsnotify_mark_destroy(void *ignored) | |
460 | { | |
461 | struct fsnotify_mark *mark, *next; | |
efa8f7e5 | 462 | struct list_head private_destroy_list; |
75c1be48 EP |
463 | |
464 | for (;;) { | |
465 | spin_lock(&destroy_lock); | |
8778abb9 AG |
466 | /* exchange the list head */ |
467 | list_replace_init(&destroy_list, &private_destroy_list); | |
75c1be48 EP |
468 | spin_unlock(&destroy_lock); |
469 | ||
470 | synchronize_srcu(&fsnotify_mark_srcu); | |
471 | ||
37d469e7 JK |
472 | list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) { |
473 | list_del_init(&mark->g_list); | |
75c1be48 EP |
474 | fsnotify_put_mark(mark); |
475 | } | |
476 | ||
477 | wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list)); | |
478 | } | |
479 | ||
480 | return 0; | |
481 | } | |
482 | ||
483 | static int __init fsnotify_mark_init(void) | |
484 | { | |
485 | struct task_struct *thread; | |
486 | ||
487 | thread = kthread_run(fsnotify_mark_destroy, NULL, | |
488 | "fsnotify_mark"); | |
489 | if (IS_ERR(thread)) | |
490 | panic("unable to start fsnotify mark destruction thread."); | |
491 | ||
492 | return 0; | |
493 | } | |
494 | device_initcall(fsnotify_mark_init); |