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/dcache.h>
20#include <linux/fs.h>
21#include <linux/gfp.h>
22#include <linux/init.h>
23#include <linux/module.h>
24#include <linux/mount.h>
25#include <linux/srcu.h>
26
27#include <linux/fsnotify_backend.h>
28#include "fsnotify.h"
29#include "../mount.h"
30
31/*
32 * Clear all of the marks on an inode when it is being evicted from core
33 */
34void __fsnotify_inode_delete(struct inode *inode)
35{
36	fsnotify_clear_marks_by_inode(inode);
37}
38EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
39
40void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
41{
42	fsnotify_clear_marks_by_mount(mnt);
43}
44
45/*
46 * Given an inode, first check if we care what happens to our children.  Inotify
47 * and dnotify both tell their parents about events.  If we care about any event
48 * on a child we run all of our children and set a dentry flag saying that the
49 * parent cares.  Thus when an event happens on a child it can quickly tell if
50 * if there is a need to find a parent and send the event to the parent.
51 */
52void __fsnotify_update_child_dentry_flags(struct inode *inode)
53{
54	struct dentry *alias;
55	int watched;
56
57	if (!S_ISDIR(inode->i_mode))
58		return;
59
60	/* determine if the children should tell inode about their events */
61	watched = fsnotify_inode_watches_children(inode);
62
63	spin_lock(&inode->i_lock);
64	/* run all of the dentries associated with this inode.  Since this is a
65	 * directory, there damn well better only be one item on this list */
66	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
67		struct dentry *child;
68
69		/* run all of the children of the original inode and fix their
70		 * d_flags to indicate parental interest (their parent is the
71		 * original inode) */
72		spin_lock(&alias->d_lock);
73		list_for_each_entry(child, &alias->d_subdirs, d_child) {
74			if (!child->d_inode)
75				continue;
76
77			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
78			if (watched)
79				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
80			else
81				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
82			spin_unlock(&child->d_lock);
83		}
84		spin_unlock(&alias->d_lock);
85	}
86	spin_unlock(&inode->i_lock);
87}
88
89/* Notify this dentry's parent about a child's events. */
90int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
91{
92	struct dentry *parent;
93	struct inode *p_inode;
94	int ret = 0;
95
96	if (!dentry)
97		dentry = path->dentry;
98
99	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
100		return 0;
101
102	parent = dget_parent(dentry);
103	p_inode = parent->d_inode;
104
105	if (unlikely(!fsnotify_inode_watches_children(p_inode)))
106		__fsnotify_update_child_dentry_flags(p_inode);
107	else if (p_inode->i_fsnotify_mask & mask) {
108		/* we are notifying a parent so come up with the new mask which
109		 * specifies these are events which came from a child. */
110		mask |= FS_EVENT_ON_CHILD;
111
112		if (path)
113			ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
114				       dentry->d_name.name, 0);
115		else
116			ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
117				       dentry->d_name.name, 0);
118	}
119
120	dput(parent);
121
122	return ret;
123}
124EXPORT_SYMBOL_GPL(__fsnotify_parent);
125
126static int send_to_group(struct inode *to_tell,
127			 struct fsnotify_mark *inode_mark,
128			 struct fsnotify_mark *vfsmount_mark,
129			 __u32 mask, void *data,
130			 int data_is, u32 cookie,
131			 const unsigned char *file_name)
132{
133	struct fsnotify_group *group = NULL;
134	__u32 inode_test_mask = 0;
135	__u32 vfsmount_test_mask = 0;
136
137	if (unlikely(!inode_mark && !vfsmount_mark)) {
138		BUG();
139		return 0;
140	}
141
142	/* clear ignored on inode modification */
143	if (mask & FS_MODIFY) {
144		if (inode_mark &&
145		    !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
146			inode_mark->ignored_mask = 0;
147		if (vfsmount_mark &&
148		    !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
149			vfsmount_mark->ignored_mask = 0;
150	}
151
152	/* does the inode mark tell us to do something? */
153	if (inode_mark) {
154		group = inode_mark->group;
155		inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
156		inode_test_mask &= inode_mark->mask;
157		inode_test_mask &= ~inode_mark->ignored_mask;
158	}
159
160	/* does the vfsmount_mark tell us to do something? */
161	if (vfsmount_mark) {
162		vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
163		group = vfsmount_mark->group;
164		vfsmount_test_mask &= vfsmount_mark->mask;
165		vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
166		if (inode_mark)
167			vfsmount_test_mask &= ~inode_mark->ignored_mask;
168	}
169
170	pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
171		 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
172		 " data=%p data_is=%d cookie=%d\n",
173		 __func__, group, to_tell, mask, inode_mark,
174		 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
175		 data_is, cookie);
176
177	if (!inode_test_mask && !vfsmount_test_mask)
178		return 0;
179
180	return group->ops->handle_event(group, to_tell, inode_mark,
181					vfsmount_mark, mask, data, data_is,
182					file_name, cookie);
183}
184
185/*
186 * This is the main call to fsnotify.  The VFS calls into hook specific functions
187 * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
188 * out to all of the registered fsnotify_group.  Those groups can then use the
189 * notification event in whatever means they feel necessary.
190 */
191int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
192	     const unsigned char *file_name, u32 cookie)
193{
194	struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
195	struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
196	struct fsnotify_group *inode_group, *vfsmount_group;
197	struct mount *mnt;
198	int idx, ret = 0;
199	/* global tests shouldn't care about events on child only the specific event */
200	__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
201
202	if (data_is == FSNOTIFY_EVENT_PATH)
203		mnt = real_mount(((struct path *)data)->mnt);
204	else
205		mnt = NULL;
206
207	/*
208	 * if this is a modify event we may need to clear the ignored masks
209	 * otherwise return if neither the inode nor the vfsmount care about
210	 * this type of event.
211	 */
212	if (!(mask & FS_MODIFY) &&
213	    !(test_mask & to_tell->i_fsnotify_mask) &&
214	    !(mnt && test_mask & mnt->mnt_fsnotify_mask))
215		return 0;
216
217	idx = srcu_read_lock(&fsnotify_mark_srcu);
218
219	if ((mask & FS_MODIFY) ||
220	    (test_mask & to_tell->i_fsnotify_mask))
221		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
222					      &fsnotify_mark_srcu);
223
224	if (mnt && ((mask & FS_MODIFY) ||
225		    (test_mask & mnt->mnt_fsnotify_mask))) {
226		vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
227						 &fsnotify_mark_srcu);
228		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
229					      &fsnotify_mark_srcu);
230	}
231
232	/*
233	 * We need to merge inode & vfsmount mark lists so that inode mark
234	 * ignore masks are properly reflected for mount mark notifications.
235	 * That's why this traversal is so complicated...
236	 */
237	while (inode_node || vfsmount_node) {
238		inode_group = NULL;
239		inode_mark = NULL;
240		vfsmount_group = NULL;
241		vfsmount_mark = NULL;
242
243		if (inode_node) {
244			inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
245						 struct fsnotify_mark, obj_list);
246			inode_group = inode_mark->group;
247		}
248
249		if (vfsmount_node) {
250			vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
251						    struct fsnotify_mark, obj_list);
252			vfsmount_group = vfsmount_mark->group;
253		}
254
255		if (inode_group && vfsmount_group) {
256			int cmp = fsnotify_compare_groups(inode_group,
257							  vfsmount_group);
258			if (cmp > 0) {
259				inode_group = NULL;
260				inode_mark = NULL;
261			} else if (cmp < 0) {
262				vfsmount_group = NULL;
263				vfsmount_mark = NULL;
264			}
265		}
266		ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
267				    data, data_is, cookie, file_name);
268
269		if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
270			goto out;
271
272		if (inode_group)
273			inode_node = srcu_dereference(inode_node->next,
274						      &fsnotify_mark_srcu);
275		if (vfsmount_group)
276			vfsmount_node = srcu_dereference(vfsmount_node->next,
277							 &fsnotify_mark_srcu);
278	}
279	ret = 0;
280out:
281	srcu_read_unlock(&fsnotify_mark_srcu, idx);
282
283	return ret;
284}
285EXPORT_SYMBOL_GPL(fsnotify);
286
287static __init int fsnotify_init(void)
288{
289	int ret;
290
291	BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
292
293	ret = init_srcu_struct(&fsnotify_mark_srcu);
294	if (ret)
295		panic("initializing fsnotify_mark_srcu");
296
297	return 0;
298}
299core_initcall(fsnotify_init);
300