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 * Trying to get rid of a group. Remove all marks, flush all events and release 44 * the group reference. 45 * Note that another thread calling fsnotify_clear_marks_by_group() may still 46 * hold a ref to the group. 47 */ 48 void fsnotify_destroy_group(struct fsnotify_group *group) 49 { 50 /* clear all inode marks for this group, attach them to destroy_list */ 51 fsnotify_detach_group_marks(group); 52 53 /* 54 * Wait for fsnotify_mark_srcu period to end and free all marks in 55 * destroy_list 56 */ 57 fsnotify_mark_destroy_list(); 58 59 /* 60 * Since we have waited for fsnotify_mark_srcu in 61 * fsnotify_mark_destroy_list() there can be no outstanding event 62 * notification against this group. So clearing the notification queue 63 * of all events is reliable now. 64 */ 65 fsnotify_flush_notify(group); 66 67 /* 68 * Destroy overflow event (we cannot use fsnotify_destroy_event() as 69 * that deliberately ignores overflow events. 70 */ 71 if (group->overflow_event) 72 group->ops->free_event(group->overflow_event); 73 74 fsnotify_put_group(group); 75 } 76 77 /* 78 * Get reference to a group. 79 */ 80 void fsnotify_get_group(struct fsnotify_group *group) 81 { 82 atomic_inc(&group->refcnt); 83 } 84 85 /* 86 * Drop a reference to a group. Free it if it's through. 87 */ 88 void fsnotify_put_group(struct fsnotify_group *group) 89 { 90 if (atomic_dec_and_test(&group->refcnt)) 91 fsnotify_final_destroy_group(group); 92 } 93 94 /* 95 * Create a new fsnotify_group and hold a reference for the group returned. 96 */ 97 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) 98 { 99 struct fsnotify_group *group; 100 101 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); 102 if (!group) 103 return ERR_PTR(-ENOMEM); 104 105 /* set to 0 when there a no external references to this group */ 106 atomic_set(&group->refcnt, 1); 107 atomic_set(&group->num_marks, 0); 108 109 mutex_init(&group->notification_mutex); 110 INIT_LIST_HEAD(&group->notification_list); 111 init_waitqueue_head(&group->notification_waitq); 112 group->max_events = UINT_MAX; 113 114 mutex_init(&group->mark_mutex); 115 INIT_LIST_HEAD(&group->marks_list); 116 117 group->ops = ops; 118 119 return group; 120 } 121 122 int fsnotify_fasync(int fd, struct file *file, int on) 123 { 124 struct fsnotify_group *group = file->private_data; 125 126 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO; 127 } 128