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
30/*
31 * Clear all of the marks on an inode when it is being evicted from core
32 */
33void __fsnotify_inode_delete(struct inode *inode)
34{
35	fsnotify_clear_marks_by_inode(inode);
36}
37EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
38
39void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
40{
41	fsnotify_clear_marks_by_mount(mnt);
42}
43
44/*
45 * Given an inode, first check if we care what happens to our children.  Inotify
46 * and dnotify both tell their parents about events.  If we care about any event
47 * on a child we run all of our children and set a dentry flag saying that the
48 * parent cares.  Thus when an event happens on a child it can quickly tell if
49 * if there is a need to find a parent and send the event to the parent.
50 */
51void __fsnotify_update_child_dentry_flags(struct inode *inode)
52{
53	struct dentry *alias;
54	int watched;
55
56	if (!S_ISDIR(inode->i_mode))
57		return;
58
59	/* determine if the children should tell inode about their events */
60	watched = fsnotify_inode_watches_children(inode);
61
62	spin_lock(&dcache_lock);
63	/* run all of the dentries associated with this inode.  Since this is a
64	 * directory, there damn well better only be one item on this list */
65	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
66		struct dentry *child;
67
68		/* run all of the children of the original inode and fix their
69		 * d_flags to indicate parental interest (their parent is the
70		 * original inode) */
71		list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
72			if (!child->d_inode)
73				continue;
74
75			spin_lock(&child->d_lock);
76			if (watched)
77				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
78			else
79				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
80			spin_unlock(&child->d_lock);
81		}
82	}
83	spin_unlock(&dcache_lock);
84}
85
86/* Notify this dentry's parent about a child's events. */
87void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
88{
89	struct dentry *parent;
90	struct inode *p_inode;
91	bool send = false;
92	bool should_update_children = false;
93
94	if (!dentry)
95		dentry = path->dentry;
96
97	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
98		return;
99
100	spin_lock(&dentry->d_lock);
101	parent = dentry->d_parent;
102	p_inode = parent->d_inode;
103
104	if (fsnotify_inode_watches_children(p_inode)) {
105		if (p_inode->i_fsnotify_mask & mask) {
106			dget(parent);
107			send = true;
108		}
109	} else {
110		/*
111		 * The parent doesn't care about events on it's children but
112		 * at least one child thought it did.  We need to run all the
113		 * children and update their d_flags to let them know p_inode
114		 * doesn't care about them any more.
115		 */
116		dget(parent);
117		should_update_children = true;
118	}
119
120	spin_unlock(&dentry->d_lock);
121
122	if (send) {
123		/* we are notifying a parent so come up with the new mask which
124		 * specifies these are events which came from a child. */
125		mask |= FS_EVENT_ON_CHILD;
126
127		if (path)
128			fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
129				 dentry->d_name.name, 0);
130		else
131			fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
132				 dentry->d_name.name, 0);
133		dput(parent);
134	}
135
136	if (unlikely(should_update_children)) {
137		__fsnotify_update_child_dentry_flags(p_inode);
138		dput(parent);
139	}
140}
141EXPORT_SYMBOL_GPL(__fsnotify_parent);
142
143static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
144			 struct fsnotify_mark *inode_mark,
145			 struct fsnotify_mark *vfsmount_mark,
146			 __u32 mask, void *data,
147			 int data_is, u32 cookie,
148			 const unsigned char *file_name,
149			 struct fsnotify_event **event)
150{
151	struct fsnotify_group *group = NULL;
152	__u32 inode_test_mask = 0;
153	__u32 vfsmount_test_mask = 0;
154
155	if (unlikely(!inode_mark && !vfsmount_mark)) {
156		BUG();
157		return 0;
158	}
159
160	/* clear ignored on inode modification */
161	if (mask & FS_MODIFY) {
162		if (inode_mark &&
163		    !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
164			inode_mark->ignored_mask = 0;
165		if (vfsmount_mark &&
166		    !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
167			vfsmount_mark->ignored_mask = 0;
168	}
169
170	/* does the inode mark tell us to do something? */
171	if (inode_mark) {
172		group = inode_mark->group;
173		inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
174		inode_test_mask &= inode_mark->mask;
175		inode_test_mask &= ~inode_mark->ignored_mask;
176	}
177
178	/* does the vfsmount_mark tell us to do something? */
179	if (vfsmount_mark) {
180		vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
181		group = vfsmount_mark->group;
182		vfsmount_test_mask &= vfsmount_mark->mask;
183		vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
184		if (inode_mark)
185			vfsmount_test_mask &= ~inode_mark->ignored_mask;
186	}
187
188	pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x inode_mark=%p"
189		 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
190		 " data=%p data_is=%d cookie=%d event=%p\n",
191		 __func__, group, to_tell, mnt, mask, inode_mark,
192		 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
193		 data_is, cookie, *event);
194
195	if (!inode_test_mask && !vfsmount_test_mask)
196		return 0;
197
198	if (group->ops->should_send_event(group, to_tell, inode_mark,
199					  vfsmount_mark, mask, data,
200					  data_is) == false)
201		return 0;
202
203	if (!*event) {
204		*event = fsnotify_create_event(to_tell, mask, data,
205						data_is, file_name,
206						cookie, GFP_KERNEL);
207		if (!*event)
208			return -ENOMEM;
209	}
210	return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
211}
212
213/*
214 * This is the main call to fsnotify.  The VFS calls into hook specific functions
215 * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
216 * out to all of the registered fsnotify_group.  Those groups can then use the
217 * notification event in whatever means they feel necessary.
218 */
219int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
220	     const unsigned char *file_name, u32 cookie)
221{
222	struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
223	struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
224	struct fsnotify_group *inode_group, *vfsmount_group;
225	struct fsnotify_event *event = NULL;
226	struct vfsmount *mnt;
227	int idx, ret = 0;
228	/* global tests shouldn't care about events on child only the specific event */
229	__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
230
231	if (data_is == FSNOTIFY_EVENT_PATH)
232		mnt = ((struct path *)data)->mnt;
233	else
234		mnt = NULL;
235
236	/*
237	 * if this is a modify event we may need to clear the ignored masks
238	 * otherwise return if neither the inode nor the vfsmount care about
239	 * this type of event.
240	 */
241	if (!(mask & FS_MODIFY) &&
242	    !(test_mask & to_tell->i_fsnotify_mask) &&
243	    !(mnt && test_mask & mnt->mnt_fsnotify_mask))
244		return 0;
245
246	idx = srcu_read_lock(&fsnotify_mark_srcu);
247
248	if ((mask & FS_MODIFY) ||
249	    (test_mask & to_tell->i_fsnotify_mask))
250		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
251					      &fsnotify_mark_srcu);
252
253	if (mnt && ((mask & FS_MODIFY) ||
254		    (test_mask & mnt->mnt_fsnotify_mask))) {
255		vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
256						 &fsnotify_mark_srcu);
257		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
258					      &fsnotify_mark_srcu);
259	}
260
261	while (inode_node || vfsmount_node) {
262		inode_group = vfsmount_group = NULL;
263
264		if (inode_node) {
265			inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
266						 struct fsnotify_mark, i.i_list);
267			inode_group = inode_mark->group;
268		}
269
270		if (vfsmount_node) {
271			vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
272							struct fsnotify_mark, m.m_list);
273			vfsmount_group = vfsmount_mark->group;
274		}
275
276		if (inode_group > vfsmount_group) {
277			/* handle inode */
278			send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
279				      data_is, cookie, file_name, &event);
280			/* we didn't use the vfsmount_mark */
281			vfsmount_group = NULL;
282		} else if (vfsmount_group > inode_group) {
283			send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
284				      data_is, cookie, file_name, &event);
285			inode_group = NULL;
286		} else {
287			send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
288				      mask, data, data_is, cookie, file_name,
289				      &event);
290		}
291
292		if (inode_group)
293			inode_node = srcu_dereference(inode_node->next,
294						      &fsnotify_mark_srcu);
295		if (vfsmount_group)
296			vfsmount_node = srcu_dereference(vfsmount_node->next,
297							 &fsnotify_mark_srcu);
298	}
299
300	srcu_read_unlock(&fsnotify_mark_srcu, idx);
301	/*
302	 * fsnotify_create_event() took a reference so the event can't be cleaned
303	 * up while we are still trying to add it to lists, drop that one.
304	 */
305	if (event)
306		fsnotify_put_event(event);
307
308	return ret;
309}
310EXPORT_SYMBOL_GPL(fsnotify);
311
312static __init int fsnotify_init(void)
313{
314	int ret;
315
316	BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
317
318	ret = init_srcu_struct(&fsnotify_mark_srcu);
319	if (ret)
320		panic("initializing fsnotify_mark_srcu");
321
322	return 0;
323}
324core_initcall(fsnotify_init);
325