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/fs.h>
20#include <linux/init.h>
21#include <linux/kernel.h>
22#include <linux/module.h>
23#include <linux/mutex.h>
24#include <linux/spinlock.h>
25
26#include <linux/atomic.h>
27
28#include <linux/fsnotify_backend.h>
29#include "fsnotify.h"
30
31#include "../internal.h"
32
33/*
34 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
35 * any notifier is interested in hearing for this inode.
36 */
37void fsnotify_recalc_inode_mask(struct inode *inode)
38{
39	spin_lock(&inode->i_lock);
40	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
41	spin_unlock(&inode->i_lock);
42
43	__fsnotify_update_child_dentry_flags(inode);
44}
45
46void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
47{
48	struct inode *inode = mark->inode;
49
50	BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
51	assert_spin_locked(&mark->lock);
52
53	spin_lock(&inode->i_lock);
54
55	hlist_del_init_rcu(&mark->obj_list);
56	mark->inode = NULL;
57
58	/*
59	 * this mark is now off the inode->i_fsnotify_marks list and we
60	 * hold the inode->i_lock, so this is the perfect time to update the
61	 * inode->i_fsnotify_mask
62	 */
63	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
64	spin_unlock(&inode->i_lock);
65}
66
67/*
68 * Given an inode, destroy all of the marks associated with that inode.
69 */
70void fsnotify_clear_marks_by_inode(struct inode *inode)
71{
72	struct fsnotify_mark *mark;
73	struct hlist_node *n;
74	LIST_HEAD(free_list);
75
76	spin_lock(&inode->i_lock);
77	hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, obj_list) {
78		list_add(&mark->free_list, &free_list);
79		hlist_del_init_rcu(&mark->obj_list);
80		fsnotify_get_mark(mark);
81	}
82	spin_unlock(&inode->i_lock);
83
84	fsnotify_destroy_marks(&free_list);
85}
86
87/*
88 * Given a group clear all of the inode marks associated with that group.
89 */
90void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
91{
92	fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
93}
94
95/*
96 * given a group and inode, find the mark associated with that combination.
97 * if found take a reference to that mark and return it, else return NULL
98 */
99struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
100					       struct inode *inode)
101{
102	struct fsnotify_mark *mark;
103
104	spin_lock(&inode->i_lock);
105	mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
106	spin_unlock(&inode->i_lock);
107
108	return mark;
109}
110
111/*
112 * If we are setting a mark mask on an inode mark we should pin the inode
113 * in memory.
114 */
115void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
116					 __u32 mask)
117{
118	struct inode *inode;
119
120	assert_spin_locked(&mark->lock);
121
122	if (mask &&
123	    mark->inode &&
124	    !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
125		mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
126		inode = igrab(mark->inode);
127		/*
128		 * we shouldn't be able to get here if the inode wasn't
129		 * already safely held in memory.  But bug in case it
130		 * ever is wrong.
131		 */
132		BUG_ON(!inode);
133	}
134}
135
136/*
137 * Attach an initialized mark to a given inode.
138 * These marks may be used for the fsnotify backend to determine which
139 * event types should be delivered to which group and for which inodes.  These
140 * marks are ordered according to priority, highest number first, and then by
141 * the group's location in memory.
142 */
143int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
144			    struct fsnotify_group *group, struct inode *inode,
145			    int allow_dups)
146{
147	int ret;
148
149	mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
150
151	BUG_ON(!mutex_is_locked(&group->mark_mutex));
152	assert_spin_locked(&mark->lock);
153
154	spin_lock(&inode->i_lock);
155	mark->inode = inode;
156	ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
157				     allow_dups);
158	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
159	spin_unlock(&inode->i_lock);
160
161	return ret;
162}
163
164/**
165 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
166 * @list: list of inodes being unmounted (sb->s_inodes)
167 *
168 * Called during unmount with no locks held, so needs to be safe against
169 * concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
170 */
171void fsnotify_unmount_inodes(struct list_head *list)
172{
173	struct inode *inode, *next_i, *need_iput = NULL;
174
175	spin_lock(&inode_sb_list_lock);
176	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
177		struct inode *need_iput_tmp;
178
179		/*
180		 * We cannot __iget() an inode in state I_FREEING,
181		 * I_WILL_FREE, or I_NEW which is fine because by that point
182		 * the inode cannot have any associated watches.
183		 */
184		spin_lock(&inode->i_lock);
185		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
186			spin_unlock(&inode->i_lock);
187			continue;
188		}
189
190		/*
191		 * If i_count is zero, the inode cannot have any watches and
192		 * doing an __iget/iput with MS_ACTIVE clear would actually
193		 * evict all inodes with zero i_count from icache which is
194		 * unnecessarily violent and may in fact be illegal to do.
195		 */
196		if (!atomic_read(&inode->i_count)) {
197			spin_unlock(&inode->i_lock);
198			continue;
199		}
200
201		need_iput_tmp = need_iput;
202		need_iput = NULL;
203
204		/* In case fsnotify_inode_delete() drops a reference. */
205		if (inode != need_iput_tmp)
206			__iget(inode);
207		else
208			need_iput_tmp = NULL;
209		spin_unlock(&inode->i_lock);
210
211		/* In case the dropping of a reference would nuke next_i. */
212		while (&next_i->i_sb_list != list) {
213			spin_lock(&next_i->i_lock);
214			if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
215						atomic_read(&next_i->i_count)) {
216				__iget(next_i);
217				need_iput = next_i;
218				spin_unlock(&next_i->i_lock);
219				break;
220			}
221			spin_unlock(&next_i->i_lock);
222			next_i = list_entry(next_i->i_sb_list.next,
223						struct inode, i_sb_list);
224		}
225
226		/*
227		 * We can safely drop inode_sb_list_lock here because either
228		 * we actually hold references on both inode and next_i or
229		 * end of list.  Also no new inodes will be added since the
230		 * umount has begun.
231		 */
232		spin_unlock(&inode_sb_list_lock);
233
234		if (need_iput_tmp)
235			iput(need_iput_tmp);
236
237		/* for each watch, send FS_UNMOUNT and then remove it */
238		fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
239
240		fsnotify_inode_delete(inode);
241
242		iput(inode);
243
244		spin_lock(&inode_sb_list_lock);
245	}
246	spin_unlock(&inode_sb_list_lock);
247}
248