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 #include <linux/list.h> 7 #include <linux/mutex.h> 8 #include <linux/slab.h> 9 #include <linux/srcu.h> 10 #include <linux/rculist.h> 11 #include <linux/wait.h> 12 #include <linux/memcontrol.h> 13 14 #include <linux/fsnotify_backend.h> 15 #include "fsnotify.h" 16 17 #include <linux/atomic.h> 18 19 /* 20 * Final freeing of a group 21 */ 22 static void fsnotify_final_destroy_group(struct fsnotify_group *group) 23 { 24 if (group->ops->free_group_priv) 25 group->ops->free_group_priv(group); 26 27 mem_cgroup_put(group->memcg); 28 29 kfree(group); 30 } 31 32 /* 33 * Stop queueing new events for this group. Once this function returns 34 * fsnotify_add_event() will not add any new events to the group's queue. 35 */ 36 void fsnotify_group_stop_queueing(struct fsnotify_group *group) 37 { 38 spin_lock(&group->notification_lock); 39 group->shutdown = true; 40 spin_unlock(&group->notification_lock); 41 } 42 43 /* 44 * Trying to get rid of a group. Remove all marks, flush all events and release 45 * the group reference. 46 * Note that another thread calling fsnotify_clear_marks_by_group() may still 47 * hold a ref to the group. 48 */ 49 void fsnotify_destroy_group(struct fsnotify_group *group) 50 { 51 /* 52 * Stop queueing new events. The code below is careful enough to not 53 * require this but fanotify needs to stop queuing events even before 54 * fsnotify_destroy_group() is called and this makes the other callers 55 * of fsnotify_destroy_group() to see the same behavior. 56 */ 57 fsnotify_group_stop_queueing(group); 58 59 /* Clear all marks for this group and queue them for destruction */ 60 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK); 61 62 /* 63 * Some marks can still be pinned when waiting for response from 64 * userspace. Wait for those now. fsnotify_prepare_user_wait() will 65 * not succeed now so this wait is race-free. 66 */ 67 wait_event(group->notification_waitq, !atomic_read(&group->user_waits)); 68 69 /* 70 * Wait until all marks get really destroyed. We could actually destroy 71 * them ourselves instead of waiting for worker to do it, however that 72 * would be racy as worker can already be processing some marks before 73 * we even entered fsnotify_destroy_group(). 74 */ 75 fsnotify_wait_marks_destroyed(); 76 77 /* 78 * Since we have waited for fsnotify_mark_srcu in 79 * fsnotify_mark_destroy_list() there can be no outstanding event 80 * notification against this group. So clearing the notification queue 81 * of all events is reliable now. 82 */ 83 fsnotify_flush_notify(group); 84 85 /* 86 * Destroy overflow event (we cannot use fsnotify_destroy_event() as 87 * that deliberately ignores overflow events. 88 */ 89 if (group->overflow_event) 90 group->ops->free_event(group->overflow_event); 91 92 fsnotify_put_group(group); 93 } 94 95 /* 96 * Get reference to a group. 97 */ 98 void fsnotify_get_group(struct fsnotify_group *group) 99 { 100 refcount_inc(&group->refcnt); 101 } 102 103 /* 104 * Drop a reference to a group. Free it if it's through. 105 */ 106 void fsnotify_put_group(struct fsnotify_group *group) 107 { 108 if (refcount_dec_and_test(&group->refcnt)) 109 fsnotify_final_destroy_group(group); 110 } 111 112 /* 113 * Create a new fsnotify_group and hold a reference for the group returned. 114 */ 115 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) 116 { 117 struct fsnotify_group *group; 118 119 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); 120 if (!group) 121 return ERR_PTR(-ENOMEM); 122 123 /* set to 0 when there a no external references to this group */ 124 refcount_set(&group->refcnt, 1); 125 atomic_set(&group->num_marks, 0); 126 atomic_set(&group->user_waits, 0); 127 128 spin_lock_init(&group->notification_lock); 129 INIT_LIST_HEAD(&group->notification_list); 130 init_waitqueue_head(&group->notification_waitq); 131 group->max_events = UINT_MAX; 132 133 mutex_init(&group->mark_mutex); 134 INIT_LIST_HEAD(&group->marks_list); 135 136 group->ops = ops; 137 138 return group; 139 } 140 141 int fsnotify_fasync(int fd, struct file *file, int on) 142 { 143 struct fsnotify_group *group = file->private_data; 144 145 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO; 146 } 147