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 #include <linux/list.h> 20 #include <linux/mutex.h> 21 #include <linux/slab.h> 22 #include <linux/srcu.h> 23 #include <linux/rculist.h> 24 #include <linux/wait.h> 25 26 #include <linux/fsnotify_backend.h> 27 #include "fsnotify.h" 28 29 #include <linux/atomic.h> 30 31 /* 32 * Final freeing of a group 33 */ 34 static void fsnotify_final_destroy_group(struct fsnotify_group *group) 35 { 36 if (group->ops->free_group_priv) 37 group->ops->free_group_priv(group); 38 39 kfree(group); 40 } 41 42 /* 43 * Stop queueing new events for this group. Once this function returns 44 * fsnotify_add_event() will not add any new events to the group's queue. 45 */ 46 void fsnotify_group_stop_queueing(struct fsnotify_group *group) 47 { 48 spin_lock(&group->notification_lock); 49 group->shutdown = true; 50 spin_unlock(&group->notification_lock); 51 } 52 53 /* 54 * Trying to get rid of a group. Remove all marks, flush all events and release 55 * the group reference. 56 * Note that another thread calling fsnotify_clear_marks_by_group() may still 57 * hold a ref to the group. 58 */ 59 void fsnotify_destroy_group(struct fsnotify_group *group) 60 { 61 /* 62 * Stop queueing new events. The code below is careful enough to not 63 * require this but fanotify needs to stop queuing events even before 64 * fsnotify_destroy_group() is called and this makes the other callers 65 * of fsnotify_destroy_group() to see the same behavior. 66 */ 67 fsnotify_group_stop_queueing(group); 68 69 /* Clear all marks for this group and queue them for destruction */ 70 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES); 71 72 /* 73 * Some marks can still be pinned when waiting for response from 74 * userspace. Wait for those now. fsnotify_prepare_user_wait() will 75 * not succeed now so this wait is race-free. 76 */ 77 wait_event(group->notification_waitq, !atomic_read(&group->user_waits)); 78 79 /* 80 * Wait until all marks get really destroyed. We could actually destroy 81 * them ourselves instead of waiting for worker to do it, however that 82 * would be racy as worker can already be processing some marks before 83 * we even entered fsnotify_destroy_group(). 84 */ 85 fsnotify_wait_marks_destroyed(); 86 87 /* 88 * Since we have waited for fsnotify_mark_srcu in 89 * fsnotify_mark_destroy_list() there can be no outstanding event 90 * notification against this group. So clearing the notification queue 91 * of all events is reliable now. 92 */ 93 fsnotify_flush_notify(group); 94 95 /* 96 * Destroy overflow event (we cannot use fsnotify_destroy_event() as 97 * that deliberately ignores overflow events. 98 */ 99 if (group->overflow_event) 100 group->ops->free_event(group->overflow_event); 101 102 fsnotify_put_group(group); 103 } 104 105 /* 106 * Get reference to a group. 107 */ 108 void fsnotify_get_group(struct fsnotify_group *group) 109 { 110 refcount_inc(&group->refcnt); 111 } 112 113 /* 114 * Drop a reference to a group. Free it if it's through. 115 */ 116 void fsnotify_put_group(struct fsnotify_group *group) 117 { 118 if (refcount_dec_and_test(&group->refcnt)) 119 fsnotify_final_destroy_group(group); 120 } 121 122 /* 123 * Create a new fsnotify_group and hold a reference for the group returned. 124 */ 125 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) 126 { 127 struct fsnotify_group *group; 128 129 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); 130 if (!group) 131 return ERR_PTR(-ENOMEM); 132 133 /* set to 0 when there a no external references to this group */ 134 refcount_set(&group->refcnt, 1); 135 atomic_set(&group->num_marks, 0); 136 atomic_set(&group->user_waits, 0); 137 138 spin_lock_init(&group->notification_lock); 139 INIT_LIST_HEAD(&group->notification_list); 140 init_waitqueue_head(&group->notification_waitq); 141 group->max_events = UINT_MAX; 142 143 mutex_init(&group->mark_mutex); 144 INIT_LIST_HEAD(&group->marks_list); 145 146 group->ops = ops; 147 148 return group; 149 } 150 151 int fsnotify_fasync(int fd, struct file *file, int on) 152 { 153 struct fsnotify_group *group = file->private_data; 154 155 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO; 156 } 157