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 mutex_destroy(&group->mark_mutex); 29 30 kfree(group); 31 } 32 33 /* 34 * Stop queueing new events for this group. Once this function returns 35 * fsnotify_add_event() will not add any new events to the group's queue. 36 */ 37 void fsnotify_group_stop_queueing(struct fsnotify_group *group) 38 { 39 spin_lock(&group->notification_lock); 40 group->shutdown = true; 41 spin_unlock(&group->notification_lock); 42 } 43 44 /* 45 * Trying to get rid of a group. Remove all marks, flush all events and release 46 * the group reference. 47 * Note that another thread calling fsnotify_clear_marks_by_group() may still 48 * hold a ref to the group. 49 */ 50 void fsnotify_destroy_group(struct fsnotify_group *group) 51 { 52 /* 53 * Stop queueing new events. The code below is careful enough to not 54 * require this but fanotify needs to stop queuing events even before 55 * fsnotify_destroy_group() is called and this makes the other callers 56 * of fsnotify_destroy_group() to see the same behavior. 57 */ 58 fsnotify_group_stop_queueing(group); 59 60 /* Clear all marks for this group and queue them for destruction */ 61 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK); 62 63 /* 64 * Some marks can still be pinned when waiting for response from 65 * userspace. Wait for those now. fsnotify_prepare_user_wait() will 66 * not succeed now so this wait is race-free. 67 */ 68 wait_event(group->notification_waitq, !atomic_read(&group->user_waits)); 69 70 /* 71 * Wait until all marks get really destroyed. We could actually destroy 72 * them ourselves instead of waiting for worker to do it, however that 73 * would be racy as worker can already be processing some marks before 74 * we even entered fsnotify_destroy_group(). 75 */ 76 fsnotify_wait_marks_destroyed(); 77 78 /* 79 * Since we have waited for fsnotify_mark_srcu in 80 * fsnotify_mark_destroy_list() there can be no outstanding event 81 * notification against this group. So clearing the notification queue 82 * of all events is reliable now. 83 */ 84 fsnotify_flush_notify(group); 85 86 /* 87 * Destroy overflow event (we cannot use fsnotify_destroy_event() as 88 * that deliberately ignores overflow events. 89 */ 90 if (group->overflow_event) 91 group->ops->free_event(group->overflow_event); 92 93 fsnotify_put_group(group); 94 } 95 96 /* 97 * Get reference to a group. 98 */ 99 void fsnotify_get_group(struct fsnotify_group *group) 100 { 101 refcount_inc(&group->refcnt); 102 } 103 104 /* 105 * Drop a reference to a group. Free it if it's through. 106 */ 107 void fsnotify_put_group(struct fsnotify_group *group) 108 { 109 if (refcount_dec_and_test(&group->refcnt)) 110 fsnotify_final_destroy_group(group); 111 } 112 EXPORT_SYMBOL_GPL(fsnotify_put_group); 113 114 static struct fsnotify_group *__fsnotify_alloc_group( 115 const struct fsnotify_ops *ops, gfp_t gfp) 116 { 117 struct fsnotify_group *group; 118 119 group = kzalloc(sizeof(struct fsnotify_group), gfp); 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->user_waits, 0); 126 127 spin_lock_init(&group->notification_lock); 128 INIT_LIST_HEAD(&group->notification_list); 129 init_waitqueue_head(&group->notification_waitq); 130 group->max_events = UINT_MAX; 131 132 mutex_init(&group->mark_mutex); 133 INIT_LIST_HEAD(&group->marks_list); 134 135 group->ops = ops; 136 137 return group; 138 } 139 140 /* 141 * Create a new fsnotify_group and hold a reference for the group returned. 142 */ 143 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) 144 { 145 return __fsnotify_alloc_group(ops, GFP_KERNEL); 146 } 147 EXPORT_SYMBOL_GPL(fsnotify_alloc_group); 148 149 /* 150 * Create a new fsnotify_group and hold a reference for the group returned. 151 */ 152 struct fsnotify_group *fsnotify_alloc_user_group(const struct fsnotify_ops *ops) 153 { 154 return __fsnotify_alloc_group(ops, GFP_KERNEL_ACCOUNT); 155 } 156 EXPORT_SYMBOL_GPL(fsnotify_alloc_user_group); 157 158 int fsnotify_fasync(int fd, struct file *file, int on) 159 { 160 struct fsnotify_group *group = file->private_data; 161 162 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO; 163 } 164