Branch data Line data Source code
1 : : // SPDX-License-Identifier: GPL-2.0-or-later
2 : : /*
3 : : * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
4 : : */
5 : :
6 : : /*
7 : : * fsnotify inode mark locking/lifetime/and refcnting
8 : : *
9 : : * REFCNT:
10 : : * The group->recnt and mark->refcnt tell how many "things" in the kernel
11 : : * currently are referencing the objects. Both kind of objects typically will
12 : : * live inside the kernel with a refcnt of 2, one for its creation and one for
13 : : * the reference a group and a mark hold to each other.
14 : : * If you are holding the appropriate locks, you can take a reference and the
15 : : * object itself is guaranteed to survive until the reference is dropped.
16 : : *
17 : : * LOCKING:
18 : : * There are 3 locks involved with fsnotify inode marks and they MUST be taken
19 : : * in order as follows:
20 : : *
21 : : * group->mark_mutex
22 : : * mark->lock
23 : : * mark->connector->lock
24 : : *
25 : : * group->mark_mutex protects the marks_list anchored inside a given group and
26 : : * each mark is hooked via the g_list. It also protects the groups private
27 : : * data (i.e group limits).
28 : :
29 : : * mark->lock protects the marks attributes like its masks and flags.
30 : : * Furthermore it protects the access to a reference of the group that the mark
31 : : * is assigned to as well as the access to a reference of the inode/vfsmount
32 : : * that is being watched by the mark.
33 : : *
34 : : * mark->connector->lock protects the list of marks anchored inside an
35 : : * inode / vfsmount and each mark is hooked via the i_list.
36 : : *
37 : : * A list of notification marks relating to inode / mnt is contained in
38 : : * fsnotify_mark_connector. That structure is alive as long as there are any
39 : : * marks in the list and is also protected by fsnotify_mark_srcu. A mark gets
40 : : * detached from fsnotify_mark_connector when last reference to the mark is
41 : : * dropped. Thus having mark reference is enough to protect mark->connector
42 : : * pointer and to make sure fsnotify_mark_connector cannot disappear. Also
43 : : * because we remove mark from g_list before dropping mark reference associated
44 : : * with that, any mark found through g_list is guaranteed to have
45 : : * mark->connector set until we drop group->mark_mutex.
46 : : *
47 : : * LIFETIME:
48 : : * Inode marks survive between when they are added to an inode and when their
49 : : * refcnt==0. Marks are also protected by fsnotify_mark_srcu.
50 : : *
51 : : * The inode mark can be cleared for a number of different reasons including:
52 : : * - The inode is unlinked for the last time. (fsnotify_inode_remove)
53 : : * - The inode is being evicted from cache. (fsnotify_inode_delete)
54 : : * - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
55 : : * - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
56 : : * - The fsnotify_group associated with the mark is going away and all such marks
57 : : * need to be cleaned up. (fsnotify_clear_marks_by_group)
58 : : *
59 : : * This has the very interesting property of being able to run concurrently with
60 : : * any (or all) other directions.
61 : : */
62 : :
63 : : #include <linux/fs.h>
64 : : #include <linux/init.h>
65 : : #include <linux/kernel.h>
66 : : #include <linux/kthread.h>
67 : : #include <linux/module.h>
68 : : #include <linux/mutex.h>
69 : : #include <linux/slab.h>
70 : : #include <linux/spinlock.h>
71 : : #include <linux/srcu.h>
72 : : #include <linux/ratelimit.h>
73 : :
74 : : #include <linux/atomic.h>
75 : :
76 : : #include <linux/fsnotify_backend.h>
77 : : #include "fsnotify.h"
78 : :
79 : : #define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */
80 : :
81 : : struct srcu_struct fsnotify_mark_srcu;
82 : : struct kmem_cache *fsnotify_mark_connector_cachep;
83 : :
84 : : static DEFINE_SPINLOCK(destroy_lock);
85 : : static LIST_HEAD(destroy_list);
86 : : static struct fsnotify_mark_connector *connector_destroy_list;
87 : :
88 : : static void fsnotify_mark_destroy_workfn(struct work_struct *work);
89 : : static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
90 : :
91 : : static void fsnotify_connector_destroy_workfn(struct work_struct *work);
92 : : static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
93 : :
94 : 92201 : void fsnotify_get_mark(struct fsnotify_mark *mark)
95 : : {
96 [ - + # # ]: 92201 : WARN_ON_ONCE(!refcount_read(&mark->refcnt));
97 : 92201 : refcount_inc(&mark->refcnt);
98 : 92201 : }
99 : :
100 : : static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
101 : : {
102 [ + - # # ]: 37937 : if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
103 : 37937 : return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
104 [ # # # # ]: 0 : else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
105 : 0 : return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
106 [ # # # # ]: 0 : else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
107 : 0 : return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
108 : : return NULL;
109 : : }
110 : :
111 : 0 : __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
112 : : {
113 [ # # # # ]: 0 : if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
114 : : return 0;
115 : :
116 : 0 : return *fsnotify_conn_mask_p(conn);
117 : : }
118 : :
119 : 37937 : static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
120 : : {
121 : : u32 new_mask = 0;
122 : : struct fsnotify_mark *mark;
123 : :
124 [ - + ]: 37937 : assert_spin_locked(&conn->lock);
125 : : /* We can get detached connector here when inode is getting unlinked. */
126 [ + - ]: 37937 : if (!fsnotify_valid_obj_type(conn->type))
127 : 37937 : return;
128 [ + - + + : 85012 : hlist_for_each_entry(mark, &conn->list, obj_list) {
+ + ]
129 [ + - ]: 47075 : if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)
130 : 47075 : new_mask |= mark->mask;
131 : : }
132 : 37937 : *fsnotify_conn_mask_p(conn) = new_mask;
133 : : }
134 : :
135 : : /*
136 : : * Calculate mask of events for a list of marks. The caller must make sure
137 : : * connector and connector->obj cannot disappear under us. Callers achieve
138 : : * this by holding a mark->lock or mark->group->mark_mutex for a mark on this
139 : : * list.
140 : : */
141 : 36250 : void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
142 : : {
143 [ + - ]: 36250 : if (!conn)
144 : 36250 : return;
145 : :
146 : : spin_lock(&conn->lock);
147 : 36250 : __fsnotify_recalc_mask(conn);
148 : : spin_unlock(&conn->lock);
149 [ + - ]: 36250 : if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
150 : 36250 : __fsnotify_update_child_dentry_flags(
151 : : fsnotify_conn_inode(conn));
152 : : }
153 : :
154 : : /* Free all connectors queued for freeing once SRCU period ends */
155 : 7852 : static void fsnotify_connector_destroy_workfn(struct work_struct *work)
156 : : {
157 : : struct fsnotify_mark_connector *conn, *free;
158 : :
159 : : spin_lock(&destroy_lock);
160 : 7852 : conn = connector_destroy_list;
161 : 7852 : connector_destroy_list = NULL;
162 : : spin_unlock(&destroy_lock);
163 : :
164 : 7852 : synchronize_srcu(&fsnotify_mark_srcu);
165 [ + + ]: 23772 : while (conn) {
166 : : free = conn;
167 : 8068 : conn = conn->destroy_next;
168 : 8068 : kmem_cache_free(fsnotify_mark_connector_cachep, free);
169 : : }
170 : 7852 : }
171 : :
172 : 8068 : static void *fsnotify_detach_connector_from_object(
173 : : struct fsnotify_mark_connector *conn,
174 : : unsigned int *type)
175 : : {
176 : : struct inode *inode = NULL;
177 : :
178 : 8068 : *type = conn->type;
179 [ + - ]: 8068 : if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
180 : : return NULL;
181 : :
182 [ + - ]: 8068 : if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
183 : : inode = fsnotify_conn_inode(conn);
184 : 8068 : inode->i_fsnotify_mask = 0;
185 : 8068 : atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
186 [ # # ]: 0 : } else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
187 : 0 : fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
188 [ # # ]: 0 : } else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
189 : 0 : fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
190 : : }
191 : :
192 : 8068 : rcu_assign_pointer(*(conn->obj), NULL);
193 : 8068 : conn->obj = NULL;
194 : 8068 : conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
195 : :
196 : 8068 : return inode;
197 : : }
198 : :
199 : 9755 : static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
200 : : {
201 : 9755 : struct fsnotify_group *group = mark->group;
202 : :
203 [ - + # # : 9755 : if (WARN_ON_ONCE(!group))
+ - ]
204 : 9755 : return;
205 : 9755 : group->ops->free_mark(mark);
206 : 9755 : fsnotify_put_group(group);
207 : : }
208 : :
209 : : /* Drop object reference originally held by a connector */
210 : 9755 : static void fsnotify_drop_object(unsigned int type, void *objp)
211 : : {
212 : : struct inode *inode;
213 : : struct super_block *sb;
214 : :
215 [ + + ]: 9755 : if (!objp)
216 : : return;
217 : : /* Currently only inode references are passed to be dropped */
218 [ - + # # : 8068 : if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
+ - ]
219 : : return;
220 : : inode = objp;
221 : 8068 : sb = inode->i_sb;
222 : 8068 : iput(inode);
223 [ + - ]: 16136 : if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
224 : 8068 : wake_up_var(&sb->s_fsnotify_inode_refs);
225 : : }
226 : :
227 : 76703 : void fsnotify_put_mark(struct fsnotify_mark *mark)
228 : : {
229 : 76703 : struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
230 : : void *objp = NULL;
231 : 76703 : unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
232 : : bool free_conn = false;
233 : :
234 : : /* Catch marks that were actually never attached to object */
235 [ - + ]: 76703 : if (!conn) {
236 [ # # ]: 0 : if (refcount_dec_and_test(&mark->refcnt))
237 : 0 : fsnotify_final_mark_destroy(mark);
238 : 66948 : return;
239 : : }
240 : :
241 : : /*
242 : : * We have to be careful so that traversals of obj_list under lock can
243 : : * safely grab mark reference.
244 : : */
245 [ + + ]: 76703 : if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
246 : : return;
247 : :
248 : : hlist_del_init_rcu(&mark->obj_list);
249 [ + + ]: 9755 : if (hlist_empty(&conn->list)) {
250 : 8068 : objp = fsnotify_detach_connector_from_object(conn, &type);
251 : : free_conn = true;
252 : : } else {
253 : 1687 : __fsnotify_recalc_mask(conn);
254 : : }
255 : : WRITE_ONCE(mark->connector, NULL);
256 : : spin_unlock(&conn->lock);
257 : :
258 : 9755 : fsnotify_drop_object(type, objp);
259 : :
260 [ + + ]: 9755 : if (free_conn) {
261 : : spin_lock(&destroy_lock);
262 : 8068 : conn->destroy_next = connector_destroy_list;
263 : 8068 : connector_destroy_list = conn;
264 : : spin_unlock(&destroy_lock);
265 : 8068 : queue_work(system_unbound_wq, &connector_reaper_work);
266 : : }
267 : : /*
268 : : * Note that we didn't update flags telling whether inode cares about
269 : : * what's happening with children. We update these flags from
270 : : * __fsnotify_parent() lazily when next event happens on one of our
271 : : * children.
272 : : */
273 : : spin_lock(&destroy_lock);
274 : 9755 : list_add(&mark->g_list, &destroy_list);
275 : : spin_unlock(&destroy_lock);
276 : 9755 : queue_delayed_work(system_unbound_wq, &reaper_work,
277 : : FSNOTIFY_REAPER_DELAY);
278 : : }
279 : : EXPORT_SYMBOL_GPL(fsnotify_put_mark);
280 : :
281 : : /*
282 : : * Get mark reference when we found the mark via lockless traversal of object
283 : : * list. Mark can be already removed from the list by now and on its way to be
284 : : * destroyed once SRCU period ends.
285 : : *
286 : : * Also pin the group so it doesn't disappear under us.
287 : : */
288 : 0 : static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
289 : : {
290 [ # # ]: 0 : if (!mark)
291 : : return true;
292 : :
293 [ # # ]: 0 : if (refcount_inc_not_zero(&mark->refcnt)) {
294 : : spin_lock(&mark->lock);
295 [ # # ]: 0 : if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
296 : : /* mark is attached, group is still alive then */
297 : 0 : atomic_inc(&mark->group->user_waits);
298 : : spin_unlock(&mark->lock);
299 : 0 : return true;
300 : : }
301 : : spin_unlock(&mark->lock);
302 : 0 : fsnotify_put_mark(mark);
303 : : }
304 : : return false;
305 : : }
306 : :
307 : : /*
308 : : * Puts marks and wakes up group destruction if necessary.
309 : : *
310 : : * Pairs with fsnotify_get_mark_safe()
311 : : */
312 : 0 : static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
313 : : {
314 [ # # ]: 0 : if (mark) {
315 : 0 : struct fsnotify_group *group = mark->group;
316 : :
317 : 0 : fsnotify_put_mark(mark);
318 : : /*
319 : : * We abuse notification_waitq on group shutdown for waiting for
320 : : * all marks pinned when waiting for userspace.
321 : : */
322 [ # # # # ]: 0 : if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
323 : 0 : wake_up(&group->notification_waitq);
324 : : }
325 : 0 : }
326 : :
327 : 0 : bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
328 : : {
329 : : int type;
330 : :
331 [ # # ]: 0 : fsnotify_foreach_obj_type(type) {
332 : : /* This can fail if mark is being removed */
333 [ # # ]: 0 : if (!fsnotify_get_mark_safe(iter_info->marks[type]))
334 : : goto fail;
335 : : }
336 : :
337 : : /*
338 : : * Now that both marks are pinned by refcount in the inode / vfsmount
339 : : * lists, we can drop SRCU lock, and safely resume the list iteration
340 : : * once userspace returns.
341 : : */
342 : 0 : srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
343 : :
344 : 0 : return true;
345 : :
346 : : fail:
347 [ # # ]: 0 : for (type--; type >= 0; type--)
348 : 0 : fsnotify_put_mark_wake(iter_info->marks[type]);
349 : : return false;
350 : : }
351 : :
352 : 0 : void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
353 : : {
354 : : int type;
355 : :
356 : 0 : iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
357 [ # # ]: 0 : fsnotify_foreach_obj_type(type)
358 : 0 : fsnotify_put_mark_wake(iter_info->marks[type]);
359 : 0 : }
360 : :
361 : : /*
362 : : * Mark mark as detached, remove it from group list. Mark still stays in object
363 : : * list until its last reference is dropped. Note that we rely on mark being
364 : : * removed from group list before corresponding reference to it is dropped. In
365 : : * particular we rely on mark->connector being valid while we hold
366 : : * group->mark_mutex if we found the mark through g_list.
367 : : *
368 : : * Must be called with group->mark_mutex held. The caller must either hold
369 : : * reference to the mark or be protected by fsnotify_mark_srcu.
370 : : */
371 : 9755 : void fsnotify_detach_mark(struct fsnotify_mark *mark)
372 : : {
373 : 9755 : struct fsnotify_group *group = mark->group;
374 : :
375 [ - + # # ]: 9755 : WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
376 : : WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
377 : : refcount_read(&mark->refcnt) < 1 +
378 : : !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
379 : :
380 : : spin_lock(&mark->lock);
381 : : /* something else already called this function on this mark */
382 [ - + ]: 9755 : if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
383 : : spin_unlock(&mark->lock);
384 : 9755 : return;
385 : : }
386 : 9755 : mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
387 : 9755 : list_del_init(&mark->g_list);
388 : : spin_unlock(&mark->lock);
389 : :
390 : 9755 : atomic_dec(&group->num_marks);
391 : :
392 : : /* Drop mark reference acquired in fsnotify_add_mark_locked() */
393 : 9755 : fsnotify_put_mark(mark);
394 : : }
395 : :
396 : : /*
397 : : * Free fsnotify mark. The mark is actually only marked as being freed. The
398 : : * freeing is actually happening only once last reference to the mark is
399 : : * dropped from a workqueue which first waits for srcu period end.
400 : : *
401 : : * Caller must have a reference to the mark or be protected by
402 : : * fsnotify_mark_srcu.
403 : : */
404 : 9755 : void fsnotify_free_mark(struct fsnotify_mark *mark)
405 : : {
406 : 9755 : struct fsnotify_group *group = mark->group;
407 : :
408 : : spin_lock(&mark->lock);
409 : : /* something else already called this function on this mark */
410 [ - + ]: 9755 : if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
411 : : spin_unlock(&mark->lock);
412 : 9755 : return;
413 : : }
414 : 9755 : mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
415 : : spin_unlock(&mark->lock);
416 : :
417 : : /*
418 : : * Some groups like to know that marks are being freed. This is a
419 : : * callback to the group function to let it know that this mark
420 : : * is being freed.
421 : : */
422 [ + - ]: 9755 : if (group->ops->freeing_mark)
423 : 9755 : group->ops->freeing_mark(mark, group);
424 : : }
425 : :
426 : 9114 : void fsnotify_destroy_mark(struct fsnotify_mark *mark,
427 : : struct fsnotify_group *group)
428 : : {
429 : 9114 : mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
430 : 9114 : fsnotify_detach_mark(mark);
431 : 9114 : mutex_unlock(&group->mark_mutex);
432 : 9114 : fsnotify_free_mark(mark);
433 : 9114 : }
434 : : EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
435 : :
436 : : /*
437 : : * Sorting function for lists of fsnotify marks.
438 : : *
439 : : * Fanotify supports different notification classes (reflected as priority of
440 : : * notification group). Events shall be passed to notification groups in
441 : : * decreasing priority order. To achieve this marks in notification lists for
442 : : * inodes and vfsmounts are sorted so that priorities of corresponding groups
443 : : * are descending.
444 : : *
445 : : * Furthermore correct handling of the ignore mask requires processing inode
446 : : * and vfsmount marks of each group together. Using the group address as
447 : : * further sort criterion provides a unique sorting order and thus we can
448 : : * merge inode and vfsmount lists of marks in linear time and find groups
449 : : * present in both lists.
450 : : *
451 : : * A return value of 1 signifies that b has priority over a.
452 : : * A return value of 0 signifies that the two marks have to be handled together.
453 : : * A return value of -1 signifies that a has priority over b.
454 : : */
455 : 67796 : int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
456 : : {
457 [ + - + + ]: 74903 : if (a == b)
458 : : return 0;
459 [ + - - + ]: 41005 : if (!a)
460 : : return 1;
461 [ + - # # ]: 7107 : if (!b)
462 : : return -1;
463 [ + - # # ]: 7107 : if (a->priority < b->priority)
464 : : return 1;
465 [ + - # # ]: 7107 : if (a->priority > b->priority)
466 : : return -1;
467 [ + + # # ]: 7107 : if (a < b)
468 : : return 1;
469 : 0 : return -1;
470 : : }
471 : :
472 : 29803 : static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
473 : : unsigned int type,
474 : : __kernel_fsid_t *fsid)
475 : : {
476 : : struct inode *inode = NULL;
477 : : struct fsnotify_mark_connector *conn;
478 : :
479 : 29803 : conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
480 [ + - ]: 29803 : if (!conn)
481 : : return -ENOMEM;
482 : 29803 : spin_lock_init(&conn->lock);
483 : 29803 : INIT_HLIST_HEAD(&conn->list);
484 : 29803 : conn->type = type;
485 : 29803 : conn->obj = connp;
486 : : /* Cache fsid of filesystem containing the object */
487 [ - + ]: 29803 : if (fsid) {
488 : 0 : conn->fsid = *fsid;
489 : 0 : conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
490 : : } else {
491 : 29803 : conn->fsid.val[0] = conn->fsid.val[1] = 0;
492 : 29803 : conn->flags = 0;
493 : : }
494 [ + - ]: 29803 : if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
495 : 29803 : inode = igrab(fsnotify_conn_inode(conn));
496 : : /*
497 : : * cmpxchg() provides the barrier so that readers of *connp can see
498 : : * only initialized structure
499 : : */
500 [ + + ]: 29803 : if (cmpxchg(connp, NULL, conn)) {
501 : : /* Someone else created list structure for us */
502 [ + - ]: 1 : if (inode)
503 : 1 : iput(inode);
504 : 1 : kmem_cache_free(fsnotify_mark_connector_cachep, conn);
505 : : }
506 : :
507 : : return 0;
508 : : }
509 : :
510 : : /*
511 : : * Get mark connector, make sure it is alive and return with its lock held.
512 : : * This is for users that get connector pointer from inode or mount. Users that
513 : : * hold reference to a mark on the list may directly lock connector->lock as
514 : : * they are sure list cannot go away under them.
515 : : */
516 : 3432410 : static struct fsnotify_mark_connector *fsnotify_grab_connector(
517 : : fsnotify_connp_t *connp)
518 : : {
519 : : struct fsnotify_mark_connector *conn;
520 : : int idx;
521 : :
522 : : idx = srcu_read_lock(&fsnotify_mark_srcu);
523 : 3432382 : conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
524 [ + + ]: 3432382 : if (!conn)
525 : : goto out;
526 : : spin_lock(&conn->lock);
527 [ - + ]: 48681 : if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
528 : : spin_unlock(&conn->lock);
529 : 0 : srcu_read_unlock(&fsnotify_mark_srcu, idx);
530 : 0 : return NULL;
531 : : }
532 : : out:
533 : 3432382 : srcu_read_unlock(&fsnotify_mark_srcu, idx);
534 : 3431549 : return conn;
535 : : }
536 : :
537 : : /*
538 : : * Add mark into proper place in given list of marks. These marks may be used
539 : : * for the fsnotify backend to determine which event types should be delivered
540 : : * to which group and for which inodes. These marks are ordered according to
541 : : * priority, highest number first, and then by the group's location in memory.
542 : : */
543 : 35008 : static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
544 : : fsnotify_connp_t *connp, unsigned int type,
545 : : int allow_dups, __kernel_fsid_t *fsid)
546 : : {
547 : : struct fsnotify_mark *lmark, *last = NULL;
548 : : struct fsnotify_mark_connector *conn;
549 : : int cmp;
550 : : int err = 0;
551 : :
552 [ - + + - ]: 35008 : if (WARN_ON(!fsnotify_valid_obj_type(type)))
553 : : return -EINVAL;
554 : :
555 : : /* Backend is expected to check for zero fsid (e.g. tmpfs) */
556 [ - + # # : 35008 : if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
# # # # #
# - - ]
557 : : return -ENODEV;
558 : :
559 : : restart:
560 : : spin_lock(&mark->lock);
561 : 64811 : conn = fsnotify_grab_connector(connp);
562 [ + + ]: 64810 : if (!conn) {
563 : : spin_unlock(&mark->lock);
564 : 29803 : err = fsnotify_attach_connector_to_object(connp, type, fsid);
565 [ + - ]: 29803 : if (err)
566 : 0 : return err;
567 : : goto restart;
568 [ - + # # ]: 35008 : } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
569 : 0 : conn->fsid = *fsid;
570 : : /* Pairs with smp_rmb() in fanotify_get_fsid() */
571 : 0 : smp_wmb();
572 : 0 : conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
573 [ - + # # : 35008 : } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
# # ]
574 [ # # ]: 0 : (fsid->val[0] != conn->fsid.val[0] ||
575 : 0 : fsid->val[1] != conn->fsid.val[1])) {
576 : : /*
577 : : * Backend is expected to check for non uniform fsid
578 : : * (e.g. btrfs), but maybe we missed something?
579 : : * Only allow setting conn->fsid once to non zero fsid.
580 : : * inotify and non-fid fanotify groups do not set nor test
581 : : * conn->fsid.
582 : : */
583 [ # # ]: 0 : pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
584 : : "%x.%x != %x.%x\n", __func__, conn->type,
585 : : fsid->val[0], fsid->val[1],
586 : : conn->fsid.val[0], conn->fsid.val[1]);
587 : : err = -EXDEV;
588 : : goto out_err;
589 : : }
590 : :
591 : : /* is mark the first mark? */
592 [ + + ]: 35008 : if (hlist_empty(&conn->list)) {
593 : 29802 : hlist_add_head_rcu(&mark->obj_list, &conn->list);
594 : : goto added;
595 : : }
596 : :
597 : : /* should mark be in the middle of the current list? */
598 [ + - + + : 9850 : hlist_for_each_entry(lmark, &conn->list, obj_list) {
+ + ]
599 : : last = lmark;
600 : :
601 [ - + # # ]: 7107 : if ((lmark->group == mark->group) &&
602 [ # # ]: 0 : (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
603 : : !allow_dups) {
604 : : err = -EEXIST;
605 : : goto out_err;
606 : : }
607 : :
608 : : cmp = fsnotify_compare_groups(lmark->group, mark->group);
609 [ + + ]: 7107 : if (cmp >= 0) {
610 : 2463 : hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
611 : : goto added;
612 : : }
613 : : }
614 : :
615 [ - + ]: 2743 : BUG_ON(last == NULL);
616 : : /* mark should be the last entry. last is the current last entry */
617 : 2743 : hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
618 : : added:
619 : : /*
620 : : * Since connector is attached to object using cmpxchg() we are
621 : : * guaranteed that connector initialization is fully visible by anyone
622 : : * seeing mark->connector set.
623 : : */
624 : 35007 : WRITE_ONCE(mark->connector, conn);
625 : : out_err:
626 : : spin_unlock(&conn->lock);
627 : : spin_unlock(&mark->lock);
628 : 35007 : return err;
629 : : }
630 : :
631 : : /*
632 : : * Attach an initialized mark to a given group and fs object.
633 : : * These marks may be used for the fsnotify backend to determine which
634 : : * event types should be delivered to which group.
635 : : */
636 : 35008 : int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
637 : : fsnotify_connp_t *connp, unsigned int type,
638 : : int allow_dups, __kernel_fsid_t *fsid)
639 : : {
640 : 35008 : struct fsnotify_group *group = mark->group;
641 : : int ret = 0;
642 : :
643 [ - + ]: 35008 : BUG_ON(!mutex_is_locked(&group->mark_mutex));
644 : :
645 : : /*
646 : : * LOCKING ORDER!!!!
647 : : * group->mark_mutex
648 : : * mark->lock
649 : : * mark->connector->lock
650 : : */
651 : : spin_lock(&mark->lock);
652 : 35008 : mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
653 : :
654 : 35008 : list_add(&mark->g_list, &group->marks_list);
655 : 35008 : atomic_inc(&group->num_marks);
656 : 35007 : fsnotify_get_mark(mark); /* for g_list */
657 : : spin_unlock(&mark->lock);
658 : :
659 : 35007 : ret = fsnotify_add_mark_list(mark, connp, type, allow_dups, fsid);
660 [ + - ]: 35008 : if (ret)
661 : : goto err;
662 : :
663 [ + - ]: 35008 : if (mark->mask)
664 : 35008 : fsnotify_recalc_mask(mark->connector);
665 : :
666 : : return ret;
667 : : err:
668 : : spin_lock(&mark->lock);
669 : 0 : mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
670 : : FSNOTIFY_MARK_FLAG_ATTACHED);
671 : : list_del_init(&mark->g_list);
672 : : spin_unlock(&mark->lock);
673 : : atomic_dec(&group->num_marks);
674 : :
675 : 0 : fsnotify_put_mark(mark);
676 : 0 : return ret;
677 : : }
678 : :
679 : 0 : int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
680 : : unsigned int type, int allow_dups, __kernel_fsid_t *fsid)
681 : : {
682 : : int ret;
683 : 0 : struct fsnotify_group *group = mark->group;
684 : :
685 : 0 : mutex_lock(&group->mark_mutex);
686 : 0 : ret = fsnotify_add_mark_locked(mark, connp, type, allow_dups, fsid);
687 : 0 : mutex_unlock(&group->mark_mutex);
688 : 0 : return ret;
689 : : }
690 : : EXPORT_SYMBOL_GPL(fsnotify_add_mark);
691 : :
692 : : /*
693 : : * Given a list of marks, find the mark associated with given group. If found
694 : : * take a reference to that mark and return it, else return NULL.
695 : : */
696 : 1579939 : struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
697 : : struct fsnotify_group *group)
698 : : {
699 : : struct fsnotify_mark_connector *conn;
700 : : struct fsnotify_mark *mark;
701 : :
702 : 1579939 : conn = fsnotify_grab_connector(connp);
703 [ + + ]: 1579890 : if (!conn)
704 : : return NULL;
705 : :
706 [ + - + + : 31432 : hlist_for_each_entry(mark, &conn->list, obj_list) {
+ + ]
707 [ + + + - ]: 23109 : if (mark->group == group &&
708 : 2675 : (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
709 : 2675 : fsnotify_get_mark(mark);
710 : : spin_unlock(&conn->lock);
711 : 2675 : return mark;
712 : : }
713 : : }
714 : : spin_unlock(&conn->lock);
715 : 10998 : return NULL;
716 : : }
717 : : EXPORT_SYMBOL_GPL(fsnotify_find_mark);
718 : :
719 : : /* Clear any marks in a group with given type mask */
720 : 1035 : void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
721 : : unsigned int type_mask)
722 : : {
723 : : struct fsnotify_mark *lmark, *mark;
724 : 1035 : LIST_HEAD(to_free);
725 : : struct list_head *head = &to_free;
726 : :
727 : : /* Skip selection step if we want to clear all marks. */
728 [ + - ]: 1035 : if (type_mask == FSNOTIFY_OBJ_ALL_TYPES_MASK) {
729 : 1035 : head = &group->marks_list;
730 : 1035 : goto clear;
731 : : }
732 : : /*
733 : : * We have to be really careful here. Anytime we drop mark_mutex, e.g.
734 : : * fsnotify_clear_marks_by_inode() can come and free marks. Even in our
735 : : * to_free list so we have to use mark_mutex even when accessing that
736 : : * list. And freeing mark requires us to drop mark_mutex. So we can
737 : : * reliably free only the first mark in the list. That's why we first
738 : : * move marks to free to to_free list in one go and then free marks in
739 : : * to_free list one by one.
740 : : */
741 : 0 : mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
742 [ # # ]: 0 : list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
743 [ # # ]: 0 : if ((1U << mark->connector->type) & type_mask)
744 : : list_move(&mark->g_list, &to_free);
745 : : }
746 : 0 : mutex_unlock(&group->mark_mutex);
747 : :
748 : : clear:
749 : : while (1) {
750 : 1676 : mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
751 [ + + ]: 1676 : if (list_empty(head)) {
752 : 1035 : mutex_unlock(&group->mark_mutex);
753 : : break;
754 : : }
755 : 641 : mark = list_first_entry(head, struct fsnotify_mark, g_list);
756 : 641 : fsnotify_get_mark(mark);
757 : 641 : fsnotify_detach_mark(mark);
758 : 641 : mutex_unlock(&group->mark_mutex);
759 : 641 : fsnotify_free_mark(mark);
760 : 641 : fsnotify_put_mark(mark);
761 : 641 : }
762 : 1035 : }
763 : :
764 : : /* Destroy all marks attached to an object via connector */
765 : 1787707 : void fsnotify_destroy_marks(fsnotify_connp_t *connp)
766 : : {
767 : : struct fsnotify_mark_connector *conn;
768 : : struct fsnotify_mark *mark, *old_mark = NULL;
769 : : void *objp;
770 : : unsigned int type;
771 : :
772 : 1787707 : conn = fsnotify_grab_connector(connp);
773 [ - + ]: 1787790 : if (!conn)
774 : 1787790 : return;
775 : : /*
776 : : * We have to be careful since we can race with e.g.
777 : : * fsnotify_clear_marks_by_group() and once we drop the conn->lock, the
778 : : * list can get modified. However we are holding mark reference and
779 : : * thus our mark cannot be removed from obj_list so we can continue
780 : : * iteration after regaining conn->lock.
781 : : */
782 [ # # # # : 0 : hlist_for_each_entry(mark, &conn->list, obj_list) {
# # ]
783 : 0 : fsnotify_get_mark(mark);
784 : : spin_unlock(&conn->lock);
785 [ # # ]: 0 : if (old_mark)
786 : 0 : fsnotify_put_mark(old_mark);
787 : : old_mark = mark;
788 : 0 : fsnotify_destroy_mark(mark, mark->group);
789 : : spin_lock(&conn->lock);
790 : : }
791 : : /*
792 : : * Detach list from object now so that we don't pin inode until all
793 : : * mark references get dropped. It would lead to strange results such
794 : : * as delaying inode deletion or blocking unmount.
795 : : */
796 : 0 : objp = fsnotify_detach_connector_from_object(conn, &type);
797 : : spin_unlock(&conn->lock);
798 [ # # ]: 0 : if (old_mark)
799 : 0 : fsnotify_put_mark(old_mark);
800 : 0 : fsnotify_drop_object(type, objp);
801 : : }
802 : :
803 : : /*
804 : : * Nothing fancy, just initialize lists and locks and counters.
805 : : */
806 : 35008 : void fsnotify_init_mark(struct fsnotify_mark *mark,
807 : : struct fsnotify_group *group)
808 : : {
809 : 35008 : memset(mark, 0, sizeof(*mark));
810 : 35008 : spin_lock_init(&mark->lock);
811 : : refcount_set(&mark->refcnt, 1);
812 : 35008 : fsnotify_get_group(group);
813 : 35008 : mark->group = group;
814 : : WRITE_ONCE(mark->connector, NULL);
815 : 35008 : }
816 : : EXPORT_SYMBOL_GPL(fsnotify_init_mark);
817 : :
818 : : /*
819 : : * Destroy all marks in destroy_list, waits for SRCU period to finish before
820 : : * actually freeing marks.
821 : : */
822 : 7929 : static void fsnotify_mark_destroy_workfn(struct work_struct *work)
823 : : {
824 : : struct fsnotify_mark *mark, *next;
825 : : struct list_head private_destroy_list;
826 : :
827 : : spin_lock(&destroy_lock);
828 : : /* exchange the list head */
829 : : list_replace_init(&destroy_list, &private_destroy_list);
830 : : spin_unlock(&destroy_lock);
831 : :
832 : 7929 : synchronize_srcu(&fsnotify_mark_srcu);
833 : :
834 [ + + ]: 17684 : list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
835 : : list_del_init(&mark->g_list);
836 : 9755 : fsnotify_final_mark_destroy(mark);
837 : : }
838 : 7929 : }
839 : :
840 : : /* Wait for all marks queued for destruction to be actually destroyed */
841 : 1035 : void fsnotify_wait_marks_destroyed(void)
842 : : {
843 : 1035 : flush_delayed_work(&reaper_work);
844 : 1035 : }
845 : : EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);
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