Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / fs / notify / fsnotify.c
blob219b269c737e6e0d85f05fb142e712c918d34dfc
1 /*
2 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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.
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.
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.
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>
27 #include <linux/fsnotify_backend.h>
28 #include "fsnotify.h"
31 * Clear all of the marks on an inode when it is being evicted from core
33 void __fsnotify_inode_delete(struct inode *inode)
35 fsnotify_clear_marks_by_inode(inode);
37 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
39 void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
41 fsnotify_clear_marks_by_mount(mnt);
44 /**
45 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
46 * @sb: superblock being unmounted.
48 * Called during unmount with no locks held, so needs to be safe against
49 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
51 void fsnotify_unmount_inodes(struct super_block *sb)
53 struct inode *inode, *iput_inode = NULL;
55 spin_lock(&sb->s_inode_list_lock);
56 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
58 * We cannot __iget() an inode in state I_FREEING,
59 * I_WILL_FREE, or I_NEW which is fine because by that point
60 * the inode cannot have any associated watches.
62 spin_lock(&inode->i_lock);
63 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
64 spin_unlock(&inode->i_lock);
65 continue;
69 * If i_count is zero, the inode cannot have any watches and
70 * doing an __iget/iput with SB_ACTIVE clear would actually
71 * evict all inodes with zero i_count from icache which is
72 * unnecessarily violent and may in fact be illegal to do.
74 if (!atomic_read(&inode->i_count)) {
75 spin_unlock(&inode->i_lock);
76 continue;
79 __iget(inode);
80 spin_unlock(&inode->i_lock);
81 spin_unlock(&sb->s_inode_list_lock);
83 if (iput_inode)
84 iput(iput_inode);
86 /* for each watch, send FS_UNMOUNT and then remove it */
87 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
89 fsnotify_inode_delete(inode);
91 iput_inode = inode;
93 spin_lock(&sb->s_inode_list_lock);
95 spin_unlock(&sb->s_inode_list_lock);
97 if (iput_inode)
98 iput(iput_inode);
102 * Given an inode, first check if we care what happens to our children. Inotify
103 * and dnotify both tell their parents about events. If we care about any event
104 * on a child we run all of our children and set a dentry flag saying that the
105 * parent cares. Thus when an event happens on a child it can quickly tell if
106 * if there is a need to find a parent and send the event to the parent.
108 void __fsnotify_update_child_dentry_flags(struct inode *inode)
110 struct dentry *alias;
111 int watched;
113 if (!S_ISDIR(inode->i_mode))
114 return;
116 /* determine if the children should tell inode about their events */
117 watched = fsnotify_inode_watches_children(inode);
119 spin_lock(&inode->i_lock);
120 /* run all of the dentries associated with this inode. Since this is a
121 * directory, there damn well better only be one item on this list */
122 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
123 struct dentry *child;
125 /* run all of the children of the original inode and fix their
126 * d_flags to indicate parental interest (their parent is the
127 * original inode) */
128 spin_lock(&alias->d_lock);
129 list_for_each_entry(child, &alias->d_subdirs, d_child) {
130 if (!child->d_inode)
131 continue;
133 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
134 if (watched)
135 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
136 else
137 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
138 spin_unlock(&child->d_lock);
140 spin_unlock(&alias->d_lock);
142 spin_unlock(&inode->i_lock);
145 /* Notify this dentry's parent about a child's events. */
146 int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
148 struct dentry *parent;
149 struct inode *p_inode;
150 int ret = 0;
152 if (!dentry)
153 dentry = path->dentry;
155 if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
156 return 0;
158 parent = dget_parent(dentry);
159 p_inode = parent->d_inode;
161 if (unlikely(!fsnotify_inode_watches_children(p_inode)))
162 __fsnotify_update_child_dentry_flags(p_inode);
163 else if (p_inode->i_fsnotify_mask & mask) {
164 struct name_snapshot name;
166 /* we are notifying a parent so come up with the new mask which
167 * specifies these are events which came from a child. */
168 mask |= FS_EVENT_ON_CHILD;
170 take_dentry_name_snapshot(&name, dentry);
171 if (path)
172 ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
173 name.name, 0);
174 else
175 ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
176 name.name, 0);
177 release_dentry_name_snapshot(&name);
180 dput(parent);
182 return ret;
184 EXPORT_SYMBOL_GPL(__fsnotify_parent);
186 static int send_to_group(struct inode *to_tell,
187 struct fsnotify_mark *inode_mark,
188 struct fsnotify_mark *vfsmount_mark,
189 __u32 mask, const void *data,
190 int data_is, u32 cookie,
191 const unsigned char *file_name,
192 struct fsnotify_iter_info *iter_info)
194 struct fsnotify_group *group = NULL;
195 __u32 inode_test_mask = 0;
196 __u32 vfsmount_test_mask = 0;
198 if (unlikely(!inode_mark && !vfsmount_mark)) {
199 BUG();
200 return 0;
203 /* clear ignored on inode modification */
204 if (mask & FS_MODIFY) {
205 if (inode_mark &&
206 !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
207 inode_mark->ignored_mask = 0;
208 if (vfsmount_mark &&
209 !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
210 vfsmount_mark->ignored_mask = 0;
213 /* does the inode mark tell us to do something? */
214 if (inode_mark) {
215 group = inode_mark->group;
216 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
217 inode_test_mask &= inode_mark->mask;
218 inode_test_mask &= ~inode_mark->ignored_mask;
221 /* does the vfsmount_mark tell us to do something? */
222 if (vfsmount_mark) {
223 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
224 group = vfsmount_mark->group;
225 vfsmount_test_mask &= vfsmount_mark->mask;
226 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
227 if (inode_mark)
228 vfsmount_test_mask &= ~inode_mark->ignored_mask;
231 pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
232 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
233 " data=%p data_is=%d cookie=%d\n",
234 __func__, group, to_tell, mask, inode_mark,
235 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
236 data_is, cookie);
238 if (!inode_test_mask && !vfsmount_test_mask)
239 return 0;
241 return group->ops->handle_event(group, to_tell, inode_mark,
242 vfsmount_mark, mask, data, data_is,
243 file_name, cookie, iter_info);
246 static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
248 struct fsnotify_mark_connector *conn;
249 struct hlist_node *node = NULL;
251 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
252 if (conn)
253 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
255 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
258 static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
260 struct hlist_node *node = NULL;
262 if (mark)
263 node = srcu_dereference(mark->obj_list.next,
264 &fsnotify_mark_srcu);
266 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
270 * This is the main call to fsnotify. The VFS calls into hook specific functions
271 * in linux/fsnotify.h. Those functions then in turn call here. Here will call
272 * out to all of the registered fsnotify_group. Those groups can then use the
273 * notification event in whatever means they feel necessary.
275 int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
276 const unsigned char *file_name, u32 cookie)
278 struct fsnotify_iter_info iter_info = {};
279 struct mount *mnt;
280 int ret = 0;
281 /* global tests shouldn't care about events on child only the specific event */
282 __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
284 if (data_is == FSNOTIFY_EVENT_PATH)
285 mnt = real_mount(((const struct path *)data)->mnt);
286 else
287 mnt = NULL;
290 * Optimization: srcu_read_lock() has a memory barrier which can
291 * be expensive. It protects walking the *_fsnotify_marks lists.
292 * However, if we do not walk the lists, we do not have to do
293 * SRCU because we have no references to any objects and do not
294 * need SRCU to keep them "alive".
296 if (!to_tell->i_fsnotify_marks &&
297 (!mnt || !mnt->mnt_fsnotify_marks))
298 return 0;
300 * if this is a modify event we may need to clear the ignored masks
301 * otherwise return if neither the inode nor the vfsmount care about
302 * this type of event.
304 if (!(mask & FS_MODIFY) &&
305 !(test_mask & to_tell->i_fsnotify_mask) &&
306 !(mnt && test_mask & mnt->mnt_fsnotify_mask))
307 return 0;
309 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
311 if ((mask & FS_MODIFY) ||
312 (test_mask & to_tell->i_fsnotify_mask)) {
313 iter_info.inode_mark =
314 fsnotify_first_mark(&to_tell->i_fsnotify_marks);
317 if (mnt && ((mask & FS_MODIFY) ||
318 (test_mask & mnt->mnt_fsnotify_mask))) {
319 iter_info.inode_mark =
320 fsnotify_first_mark(&to_tell->i_fsnotify_marks);
321 iter_info.vfsmount_mark =
322 fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
326 * We need to merge inode & vfsmount mark lists so that inode mark
327 * ignore masks are properly reflected for mount mark notifications.
328 * That's why this traversal is so complicated...
330 while (iter_info.inode_mark || iter_info.vfsmount_mark) {
331 struct fsnotify_mark *inode_mark = iter_info.inode_mark;
332 struct fsnotify_mark *vfsmount_mark = iter_info.vfsmount_mark;
334 if (inode_mark && vfsmount_mark) {
335 int cmp = fsnotify_compare_groups(inode_mark->group,
336 vfsmount_mark->group);
337 if (cmp > 0)
338 inode_mark = NULL;
339 else if (cmp < 0)
340 vfsmount_mark = NULL;
343 ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
344 data, data_is, cookie, file_name,
345 &iter_info);
347 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
348 goto out;
350 if (inode_mark)
351 iter_info.inode_mark =
352 fsnotify_next_mark(iter_info.inode_mark);
353 if (vfsmount_mark)
354 iter_info.vfsmount_mark =
355 fsnotify_next_mark(iter_info.vfsmount_mark);
357 ret = 0;
358 out:
359 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
361 return ret;
363 EXPORT_SYMBOL_GPL(fsnotify);
365 extern struct kmem_cache *fsnotify_mark_connector_cachep;
367 static __init int fsnotify_init(void)
369 int ret;
371 BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
373 ret = init_srcu_struct(&fsnotify_mark_srcu);
374 if (ret)
375 panic("initializing fsnotify_mark_srcu");
377 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
378 SLAB_PANIC);
380 return 0;
382 core_initcall(fsnotify_init);