1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
7 * fsnotify inode mark locking/lifetime/and refcnting
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.
18 * There are 3 locks involved with fsnotify inode marks and they MUST be taken
19 * in order as follows:
23 * mark->connector->lock
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).
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.
34 * mark->connector->lock protects the list of marks anchored inside an
35 * inode / vfsmount and each mark is hooked via the i_list.
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.
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.
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)
59 * This has the very interesting property of being able to run concurrently with
60 * any (or all) other directions.
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>
74 #include <linux/atomic.h>
76 #include <linux/fsnotify_backend.h>
79 #define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */
81 struct srcu_struct fsnotify_mark_srcu;
82 struct kmem_cache *fsnotify_mark_connector_cachep;
84 static DEFINE_SPINLOCK(destroy_lock);
85 static LIST_HEAD(destroy_list);
86 static struct fsnotify_mark_connector *connector_destroy_list;
88 static void fsnotify_mark_destroy_workfn(struct work_struct *work);
89 static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
91 static void fsnotify_connector_destroy_workfn(struct work_struct *work);
92 static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
94 void fsnotify_get_mark(struct fsnotify_mark *mark)
96 WARN_ON_ONCE(!refcount_read(&mark->refcnt));
97 refcount_inc(&mark->refcnt);
100 static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
102 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
103 return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
104 else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
105 return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
106 else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
107 return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
111 __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
113 if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
116 return *fsnotify_conn_mask_p(conn);
119 static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
122 struct fsnotify_mark *mark;
124 assert_spin_locked(&conn->lock);
125 /* We can get detached connector here when inode is getting unlinked. */
126 if (!fsnotify_valid_obj_type(conn->type))
128 hlist_for_each_entry(mark, &conn->list, obj_list) {
129 if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)
130 new_mask |= mark->mask;
132 *fsnotify_conn_mask_p(conn) = new_mask;
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
141 void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
146 spin_lock(&conn->lock);
147 __fsnotify_recalc_mask(conn);
148 spin_unlock(&conn->lock);
149 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
150 __fsnotify_update_child_dentry_flags(
151 fsnotify_conn_inode(conn));
154 /* Free all connectors queued for freeing once SRCU period ends */
155 static void fsnotify_connector_destroy_workfn(struct work_struct *work)
157 struct fsnotify_mark_connector *conn, *free;
159 spin_lock(&destroy_lock);
160 conn = connector_destroy_list;
161 connector_destroy_list = NULL;
162 spin_unlock(&destroy_lock);
164 synchronize_srcu(&fsnotify_mark_srcu);
167 conn = conn->destroy_next;
168 kmem_cache_free(fsnotify_mark_connector_cachep, free);
172 static void fsnotify_get_inode_ref(struct inode *inode)
175 atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
178 static void fsnotify_put_inode_ref(struct inode *inode)
180 struct super_block *sb = inode->i_sb;
183 if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
184 wake_up_var(&sb->s_fsnotify_inode_refs);
187 static void *fsnotify_detach_connector_from_object(
188 struct fsnotify_mark_connector *conn,
191 struct inode *inode = NULL;
194 if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
197 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
198 inode = fsnotify_conn_inode(conn);
199 inode->i_fsnotify_mask = 0;
200 } else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
201 fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
202 } else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
203 fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
206 rcu_assign_pointer(*(conn->obj), NULL);
208 conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
213 static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
215 struct fsnotify_group *group = mark->group;
217 if (WARN_ON_ONCE(!group))
219 group->ops->free_mark(mark);
220 fsnotify_put_group(group);
223 /* Drop object reference originally held by a connector */
224 static void fsnotify_drop_object(unsigned int type, void *objp)
228 /* Currently only inode references are passed to be dropped */
229 if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
231 fsnotify_put_inode_ref(objp);
234 void fsnotify_put_mark(struct fsnotify_mark *mark)
236 struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
238 unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
239 bool free_conn = false;
241 /* Catch marks that were actually never attached to object */
243 if (refcount_dec_and_test(&mark->refcnt))
244 fsnotify_final_mark_destroy(mark);
249 * We have to be careful so that traversals of obj_list under lock can
250 * safely grab mark reference.
252 if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
255 hlist_del_init_rcu(&mark->obj_list);
256 if (hlist_empty(&conn->list)) {
257 objp = fsnotify_detach_connector_from_object(conn, &type);
260 __fsnotify_recalc_mask(conn);
262 WRITE_ONCE(mark->connector, NULL);
263 spin_unlock(&conn->lock);
265 fsnotify_drop_object(type, objp);
268 spin_lock(&destroy_lock);
269 conn->destroy_next = connector_destroy_list;
270 connector_destroy_list = conn;
271 spin_unlock(&destroy_lock);
272 queue_work(system_unbound_wq, &connector_reaper_work);
275 * Note that we didn't update flags telling whether inode cares about
276 * what's happening with children. We update these flags from
277 * __fsnotify_parent() lazily when next event happens on one of our
280 spin_lock(&destroy_lock);
281 list_add(&mark->g_list, &destroy_list);
282 spin_unlock(&destroy_lock);
283 queue_delayed_work(system_unbound_wq, &reaper_work,
284 FSNOTIFY_REAPER_DELAY);
286 EXPORT_SYMBOL_GPL(fsnotify_put_mark);
289 * Get mark reference when we found the mark via lockless traversal of object
290 * list. Mark can be already removed from the list by now and on its way to be
291 * destroyed once SRCU period ends.
293 * Also pin the group so it doesn't disappear under us.
295 static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
300 if (refcount_inc_not_zero(&mark->refcnt)) {
301 spin_lock(&mark->lock);
302 if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
303 /* mark is attached, group is still alive then */
304 atomic_inc(&mark->group->user_waits);
305 spin_unlock(&mark->lock);
308 spin_unlock(&mark->lock);
309 fsnotify_put_mark(mark);
315 * Puts marks and wakes up group destruction if necessary.
317 * Pairs with fsnotify_get_mark_safe()
319 static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
322 struct fsnotify_group *group = mark->group;
324 fsnotify_put_mark(mark);
326 * We abuse notification_waitq on group shutdown for waiting for
327 * all marks pinned when waiting for userspace.
329 if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
330 wake_up(&group->notification_waitq);
334 bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
335 __releases(&fsnotify_mark_srcu)
339 fsnotify_foreach_obj_type(type) {
340 /* This can fail if mark is being removed */
341 if (!fsnotify_get_mark_safe(iter_info->marks[type])) {
342 __release(&fsnotify_mark_srcu);
348 * Now that both marks are pinned by refcount in the inode / vfsmount
349 * lists, we can drop SRCU lock, and safely resume the list iteration
350 * once userspace returns.
352 srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
357 for (type--; type >= 0; type--)
358 fsnotify_put_mark_wake(iter_info->marks[type]);
362 void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
363 __acquires(&fsnotify_mark_srcu)
367 iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
368 fsnotify_foreach_obj_type(type)
369 fsnotify_put_mark_wake(iter_info->marks[type]);
373 * Mark mark as detached, remove it from group list. Mark still stays in object
374 * list until its last reference is dropped. Note that we rely on mark being
375 * removed from group list before corresponding reference to it is dropped. In
376 * particular we rely on mark->connector being valid while we hold
377 * group->mark_mutex if we found the mark through g_list.
379 * Must be called with group->mark_mutex held. The caller must either hold
380 * reference to the mark or be protected by fsnotify_mark_srcu.
382 void fsnotify_detach_mark(struct fsnotify_mark *mark)
384 struct fsnotify_group *group = mark->group;
386 WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
387 WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
388 refcount_read(&mark->refcnt) < 1 +
389 !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
391 spin_lock(&mark->lock);
392 /* something else already called this function on this mark */
393 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
394 spin_unlock(&mark->lock);
397 mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
398 list_del_init(&mark->g_list);
399 spin_unlock(&mark->lock);
401 /* Drop mark reference acquired in fsnotify_add_mark_locked() */
402 fsnotify_put_mark(mark);
406 * Free fsnotify mark. The mark is actually only marked as being freed. The
407 * freeing is actually happening only once last reference to the mark is
408 * dropped from a workqueue which first waits for srcu period end.
410 * Caller must have a reference to the mark or be protected by
411 * fsnotify_mark_srcu.
413 void fsnotify_free_mark(struct fsnotify_mark *mark)
415 struct fsnotify_group *group = mark->group;
417 spin_lock(&mark->lock);
418 /* something else already called this function on this mark */
419 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
420 spin_unlock(&mark->lock);
423 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
424 spin_unlock(&mark->lock);
427 * Some groups like to know that marks are being freed. This is a
428 * callback to the group function to let it know that this mark
431 if (group->ops->freeing_mark)
432 group->ops->freeing_mark(mark, group);
435 void fsnotify_destroy_mark(struct fsnotify_mark *mark,
436 struct fsnotify_group *group)
438 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
439 fsnotify_detach_mark(mark);
440 mutex_unlock(&group->mark_mutex);
441 fsnotify_free_mark(mark);
443 EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
446 * Sorting function for lists of fsnotify marks.
448 * Fanotify supports different notification classes (reflected as priority of
449 * notification group). Events shall be passed to notification groups in
450 * decreasing priority order. To achieve this marks in notification lists for
451 * inodes and vfsmounts are sorted so that priorities of corresponding groups
454 * Furthermore correct handling of the ignore mask requires processing inode
455 * and vfsmount marks of each group together. Using the group address as
456 * further sort criterion provides a unique sorting order and thus we can
457 * merge inode and vfsmount lists of marks in linear time and find groups
458 * present in both lists.
460 * A return value of 1 signifies that b has priority over a.
461 * A return value of 0 signifies that the two marks have to be handled together.
462 * A return value of -1 signifies that a has priority over b.
464 int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
472 if (a->priority < b->priority)
474 if (a->priority > b->priority)
481 static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
483 __kernel_fsid_t *fsid)
485 struct inode *inode = NULL;
486 struct fsnotify_mark_connector *conn;
488 conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
491 spin_lock_init(&conn->lock);
492 INIT_HLIST_HEAD(&conn->list);
495 /* Cache fsid of filesystem containing the object */
498 conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
500 conn->fsid.val[0] = conn->fsid.val[1] = 0;
503 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
504 inode = fsnotify_conn_inode(conn);
505 fsnotify_get_inode_ref(inode);
509 * cmpxchg() provides the barrier so that readers of *connp can see
510 * only initialized structure
512 if (cmpxchg(connp, NULL, conn)) {
513 /* Someone else created list structure for us */
515 fsnotify_put_inode_ref(inode);
516 kmem_cache_free(fsnotify_mark_connector_cachep, conn);
523 * Get mark connector, make sure it is alive and return with its lock held.
524 * This is for users that get connector pointer from inode or mount. Users that
525 * hold reference to a mark on the list may directly lock connector->lock as
526 * they are sure list cannot go away under them.
528 static struct fsnotify_mark_connector *fsnotify_grab_connector(
529 fsnotify_connp_t *connp)
531 struct fsnotify_mark_connector *conn;
534 idx = srcu_read_lock(&fsnotify_mark_srcu);
535 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
538 spin_lock(&conn->lock);
539 if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
540 spin_unlock(&conn->lock);
541 srcu_read_unlock(&fsnotify_mark_srcu, idx);
545 srcu_read_unlock(&fsnotify_mark_srcu, idx);
550 * Add mark into proper place in given list of marks. These marks may be used
551 * for the fsnotify backend to determine which event types should be delivered
552 * to which group and for which inodes. These marks are ordered according to
553 * priority, highest number first, and then by the group's location in memory.
555 static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
556 fsnotify_connp_t *connp, unsigned int type,
557 int allow_dups, __kernel_fsid_t *fsid)
559 struct fsnotify_mark *lmark, *last = NULL;
560 struct fsnotify_mark_connector *conn;
564 if (WARN_ON(!fsnotify_valid_obj_type(type)))
567 /* Backend is expected to check for zero fsid (e.g. tmpfs) */
568 if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
572 spin_lock(&mark->lock);
573 conn = fsnotify_grab_connector(connp);
575 spin_unlock(&mark->lock);
576 err = fsnotify_attach_connector_to_object(connp, type, fsid);
580 } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
582 /* Pairs with smp_rmb() in fanotify_get_fsid() */
584 conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
585 } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
586 (fsid->val[0] != conn->fsid.val[0] ||
587 fsid->val[1] != conn->fsid.val[1])) {
589 * Backend is expected to check for non uniform fsid
590 * (e.g. btrfs), but maybe we missed something?
591 * Only allow setting conn->fsid once to non zero fsid.
592 * inotify and non-fid fanotify groups do not set nor test
595 pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
596 "%x.%x != %x.%x\n", __func__, conn->type,
597 fsid->val[0], fsid->val[1],
598 conn->fsid.val[0], conn->fsid.val[1]);
603 /* is mark the first mark? */
604 if (hlist_empty(&conn->list)) {
605 hlist_add_head_rcu(&mark->obj_list, &conn->list);
609 /* should mark be in the middle of the current list? */
610 hlist_for_each_entry(lmark, &conn->list, obj_list) {
613 if ((lmark->group == mark->group) &&
614 (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
620 cmp = fsnotify_compare_groups(lmark->group, mark->group);
622 hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
627 BUG_ON(last == NULL);
628 /* mark should be the last entry. last is the current last entry */
629 hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
632 * Since connector is attached to object using cmpxchg() we are
633 * guaranteed that connector initialization is fully visible by anyone
634 * seeing mark->connector set.
636 WRITE_ONCE(mark->connector, conn);
638 spin_unlock(&conn->lock);
639 spin_unlock(&mark->lock);
644 * Attach an initialized mark to a given group and fs object.
645 * These marks may be used for the fsnotify backend to determine which
646 * event types should be delivered to which group.
648 int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
649 fsnotify_connp_t *connp, unsigned int type,
650 int allow_dups, __kernel_fsid_t *fsid)
652 struct fsnotify_group *group = mark->group;
655 BUG_ON(!mutex_is_locked(&group->mark_mutex));
661 * mark->connector->lock
663 spin_lock(&mark->lock);
664 mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
666 list_add(&mark->g_list, &group->marks_list);
667 fsnotify_get_mark(mark); /* for g_list */
668 spin_unlock(&mark->lock);
670 ret = fsnotify_add_mark_list(mark, connp, type, allow_dups, fsid);
675 fsnotify_recalc_mask(mark->connector);
679 spin_lock(&mark->lock);
680 mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
681 FSNOTIFY_MARK_FLAG_ATTACHED);
682 list_del_init(&mark->g_list);
683 spin_unlock(&mark->lock);
685 fsnotify_put_mark(mark);
689 int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
690 unsigned int type, int allow_dups, __kernel_fsid_t *fsid)
693 struct fsnotify_group *group = mark->group;
695 mutex_lock(&group->mark_mutex);
696 ret = fsnotify_add_mark_locked(mark, connp, type, allow_dups, fsid);
697 mutex_unlock(&group->mark_mutex);
700 EXPORT_SYMBOL_GPL(fsnotify_add_mark);
703 * Given a list of marks, find the mark associated with given group. If found
704 * take a reference to that mark and return it, else return NULL.
706 struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
707 struct fsnotify_group *group)
709 struct fsnotify_mark_connector *conn;
710 struct fsnotify_mark *mark;
712 conn = fsnotify_grab_connector(connp);
716 hlist_for_each_entry(mark, &conn->list, obj_list) {
717 if (mark->group == group &&
718 (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
719 fsnotify_get_mark(mark);
720 spin_unlock(&conn->lock);
724 spin_unlock(&conn->lock);
727 EXPORT_SYMBOL_GPL(fsnotify_find_mark);
729 /* Clear any marks in a group with given type mask */
730 void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
731 unsigned int type_mask)
733 struct fsnotify_mark *lmark, *mark;
735 struct list_head *head = &to_free;
737 /* Skip selection step if we want to clear all marks. */
738 if (type_mask == FSNOTIFY_OBJ_ALL_TYPES_MASK) {
739 head = &group->marks_list;
743 * We have to be really careful here. Anytime we drop mark_mutex, e.g.
744 * fsnotify_clear_marks_by_inode() can come and free marks. Even in our
745 * to_free list so we have to use mark_mutex even when accessing that
746 * list. And freeing mark requires us to drop mark_mutex. So we can
747 * reliably free only the first mark in the list. That's why we first
748 * move marks to free to to_free list in one go and then free marks in
749 * to_free list one by one.
751 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
752 list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
753 if ((1U << mark->connector->type) & type_mask)
754 list_move(&mark->g_list, &to_free);
756 mutex_unlock(&group->mark_mutex);
760 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
761 if (list_empty(head)) {
762 mutex_unlock(&group->mark_mutex);
765 mark = list_first_entry(head, struct fsnotify_mark, g_list);
766 fsnotify_get_mark(mark);
767 fsnotify_detach_mark(mark);
768 mutex_unlock(&group->mark_mutex);
769 fsnotify_free_mark(mark);
770 fsnotify_put_mark(mark);
774 /* Destroy all marks attached to an object via connector */
775 void fsnotify_destroy_marks(fsnotify_connp_t *connp)
777 struct fsnotify_mark_connector *conn;
778 struct fsnotify_mark *mark, *old_mark = NULL;
782 conn = fsnotify_grab_connector(connp);
786 * We have to be careful since we can race with e.g.
787 * fsnotify_clear_marks_by_group() and once we drop the conn->lock, the
788 * list can get modified. However we are holding mark reference and
789 * thus our mark cannot be removed from obj_list so we can continue
790 * iteration after regaining conn->lock.
792 hlist_for_each_entry(mark, &conn->list, obj_list) {
793 fsnotify_get_mark(mark);
794 spin_unlock(&conn->lock);
796 fsnotify_put_mark(old_mark);
798 fsnotify_destroy_mark(mark, mark->group);
799 spin_lock(&conn->lock);
802 * Detach list from object now so that we don't pin inode until all
803 * mark references get dropped. It would lead to strange results such
804 * as delaying inode deletion or blocking unmount.
806 objp = fsnotify_detach_connector_from_object(conn, &type);
807 spin_unlock(&conn->lock);
809 fsnotify_put_mark(old_mark);
810 fsnotify_drop_object(type, objp);
814 * Nothing fancy, just initialize lists and locks and counters.
816 void fsnotify_init_mark(struct fsnotify_mark *mark,
817 struct fsnotify_group *group)
819 memset(mark, 0, sizeof(*mark));
820 spin_lock_init(&mark->lock);
821 refcount_set(&mark->refcnt, 1);
822 fsnotify_get_group(group);
824 WRITE_ONCE(mark->connector, NULL);
826 EXPORT_SYMBOL_GPL(fsnotify_init_mark);
829 * Destroy all marks in destroy_list, waits for SRCU period to finish before
830 * actually freeing marks.
832 static void fsnotify_mark_destroy_workfn(struct work_struct *work)
834 struct fsnotify_mark *mark, *next;
835 struct list_head private_destroy_list;
837 spin_lock(&destroy_lock);
838 /* exchange the list head */
839 list_replace_init(&destroy_list, &private_destroy_list);
840 spin_unlock(&destroy_lock);
842 synchronize_srcu(&fsnotify_mark_srcu);
844 list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
845 list_del_init(&mark->g_list);
846 fsnotify_final_mark_destroy(mark);
850 /* Wait for all marks queued for destruction to be actually destroyed */
851 void fsnotify_wait_marks_destroyed(void)
853 flush_delayed_work(&reaper_work);
855 EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);