2 * Directory notifications for Linux.
4 * Copyright (C) 2000,2001,2002 Stephen Rothwell
6 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
7 * dnotify was largly rewritten to use the new fsnotify infrastructure
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License as published by the
11 * Free Software Foundation; either version 2, or (at your option) any
14 * This program is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * General Public License for more details.
20 #include <linux/module.h>
21 #include <linux/sched.h>
22 #include <linux/sched/signal.h>
23 #include <linux/dnotify.h>
24 #include <linux/init.h>
25 #include <linux/spinlock.h>
26 #include <linux/slab.h>
27 #include <linux/fdtable.h>
28 #include <linux/fsnotify_backend.h>
30 int dir_notify_enable __read_mostly = 1;
32 static struct kmem_cache *dnotify_struct_cache __read_mostly;
33 static struct kmem_cache *dnotify_mark_cache __read_mostly;
34 static struct fsnotify_group *dnotify_group __read_mostly;
37 * dnotify will attach one of these to each inode (i_fsnotify_marks) which
38 * is being watched by dnotify. If multiple userspace applications are watching
39 * the same directory with dnotify their information is chained in dn
42 struct fsnotify_mark fsn_mark;
43 struct dnotify_struct *dn;
47 * When a process starts or stops watching an inode the set of events which
48 * dnotify cares about for that inode may change. This function runs the
49 * list of everything receiving dnotify events about this directory and calculates
50 * the set of all those events. After it updates what dnotify is interested in
51 * it calls the fsnotify function so it can update the set of all events relevant
54 static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
57 struct dnotify_struct *dn;
58 struct dnotify_mark *dn_mark = container_of(fsn_mark,
62 assert_spin_locked(&fsn_mark->lock);
64 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
65 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
66 if (fsn_mark->mask == new_mask)
68 fsn_mark->mask = new_mask;
70 fsnotify_recalc_mask(fsn_mark->connector);
74 * Mains fsnotify call where events are delivered to dnotify.
75 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
76 * on that mark and determine which of them has expressed interest in receiving
77 * events of this type. When found send the correct process and signal and
78 * destroy the dnotify struct if it was not registered to receive multiple
81 static int dnotify_handle_event(struct fsnotify_group *group,
83 u32 mask, const void *data, int data_type,
84 const unsigned char *file_name, u32 cookie,
85 struct fsnotify_iter_info *iter_info)
87 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
88 struct dnotify_mark *dn_mark;
89 struct dnotify_struct *dn;
90 struct dnotify_struct **prev;
91 struct fown_struct *fown;
92 __u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
94 /* not a dir, dnotify doesn't care */
95 if (!S_ISDIR(inode->i_mode))
98 if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
101 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
103 spin_lock(&inode_mark->lock);
105 while ((dn = *prev) != NULL) {
106 if ((dn->dn_mask & test_mask) == 0) {
110 fown = &dn->dn_filp->f_owner;
111 send_sigio(fown, dn->dn_fd, POLL_MSG);
112 if (dn->dn_mask & FS_DN_MULTISHOT)
116 kmem_cache_free(dnotify_struct_cache, dn);
117 dnotify_recalc_inode_mask(inode_mark);
121 spin_unlock(&inode_mark->lock);
126 static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
128 struct dnotify_mark *dn_mark = container_of(fsn_mark,
134 kmem_cache_free(dnotify_mark_cache, dn_mark);
137 static const struct fsnotify_ops dnotify_fsnotify_ops = {
138 .handle_event = dnotify_handle_event,
139 .free_mark = dnotify_free_mark,
143 * Called every time a file is closed. Looks first for a dnotify mark on the
144 * inode. If one is found run all of the ->dn structures attached to that
145 * mark for one relevant to this process closing the file and remove that
146 * dnotify_struct. If that was the last dnotify_struct also remove the
149 void dnotify_flush(struct file *filp, fl_owner_t id)
151 struct fsnotify_mark *fsn_mark;
152 struct dnotify_mark *dn_mark;
153 struct dnotify_struct *dn;
154 struct dnotify_struct **prev;
158 inode = file_inode(filp);
159 if (!S_ISDIR(inode->i_mode))
162 fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group);
165 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
167 mutex_lock(&dnotify_group->mark_mutex);
169 spin_lock(&fsn_mark->lock);
171 while ((dn = *prev) != NULL) {
172 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
174 kmem_cache_free(dnotify_struct_cache, dn);
175 dnotify_recalc_inode_mask(fsn_mark);
181 spin_unlock(&fsn_mark->lock);
183 /* nothing else could have found us thanks to the dnotify_groups
185 if (dn_mark->dn == NULL) {
186 fsnotify_detach_mark(fsn_mark);
190 mutex_unlock(&dnotify_group->mark_mutex);
193 fsnotify_free_mark(fsn_mark);
194 fsnotify_put_mark(fsn_mark);
197 /* this conversion is done only at watch creation */
198 static __u32 convert_arg(unsigned long arg)
200 __u32 new_mask = FS_EVENT_ON_CHILD;
202 if (arg & DN_MULTISHOT)
203 new_mask |= FS_DN_MULTISHOT;
205 new_mask |= (FS_DELETE | FS_MOVED_FROM);
207 new_mask |= FS_MODIFY;
209 new_mask |= FS_ACCESS;
211 new_mask |= FS_ATTRIB;
213 new_mask |= FS_DN_RENAME;
215 new_mask |= (FS_CREATE | FS_MOVED_TO);
221 * If multiple processes watch the same inode with dnotify there is only one
222 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
223 * onto that mark. This function either attaches the new dnotify_struct onto
224 * that list, or it |= the mask onto an existing dnofiy_struct.
226 static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
227 fl_owner_t id, int fd, struct file *filp, __u32 mask)
229 struct dnotify_struct *odn;
232 while (odn != NULL) {
233 /* adding more events to existing dnofiy_struct? */
234 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
236 odn->dn_mask |= mask;
246 dn->dn_next = dn_mark->dn;
253 * When a process calls fcntl to attach a dnotify watch to a directory it ends
254 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
255 * attached to the fsnotify_mark.
257 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
259 struct dnotify_mark *new_dn_mark, *dn_mark;
260 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
261 struct dnotify_struct *dn;
263 fl_owner_t id = current->files;
265 int destroy = 0, error = 0;
268 /* we use these to tell if we need to kfree */
272 if (!dir_notify_enable) {
277 /* a 0 mask means we are explicitly removing the watch */
278 if ((arg & ~DN_MULTISHOT) == 0) {
279 dnotify_flush(filp, id);
284 /* dnotify only works on directories */
285 inode = file_inode(filp);
286 if (!S_ISDIR(inode->i_mode)) {
291 /* expect most fcntl to add new rather than augment old */
292 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
298 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
299 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
305 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
306 mask = convert_arg(arg);
308 /* set up the new_fsn_mark and new_dn_mark */
309 new_fsn_mark = &new_dn_mark->fsn_mark;
310 fsnotify_init_mark(new_fsn_mark, dnotify_group);
311 new_fsn_mark->mask = mask;
312 new_dn_mark->dn = NULL;
314 /* this is needed to prevent the fcntl/close race described below */
315 mutex_lock(&dnotify_group->mark_mutex);
317 /* add the new_fsn_mark or find an old one. */
318 fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group);
320 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
321 spin_lock(&fsn_mark->lock);
323 error = fsnotify_add_inode_mark_locked(new_fsn_mark, inode, 0);
325 mutex_unlock(&dnotify_group->mark_mutex);
328 spin_lock(&new_fsn_mark->lock);
329 fsn_mark = new_fsn_mark;
330 dn_mark = new_dn_mark;
331 /* we used new_fsn_mark, so don't free it */
339 /* if (f != filp) means that we lost a race and another task/thread
340 * actually closed the fd we are still playing with before we grabbed
341 * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
342 * fd is the only time we clean up the marks we need to get our mark
345 /* if we added ourselves, shoot ourselves, it's possible that
346 * the flush actually did shoot this fsn_mark. That's fine too
347 * since multiple calls to destroy_mark is perfectly safe, if
348 * we found a dn_mark already attached to the inode, just sod
349 * off silently as the flush at close time dealt with it.
351 if (dn_mark == new_dn_mark)
357 __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0);
359 error = attach_dn(dn, dn_mark, id, fd, filp, mask);
360 /* !error means that we attached the dn to the dn_mark, so don't free it */
363 /* -EEXIST means that we didn't add this new dn and used an old one.
364 * that isn't an error (and the unused dn should be freed) */
365 else if (error == -EEXIST)
368 dnotify_recalc_inode_mask(fsn_mark);
370 spin_unlock(&fsn_mark->lock);
373 fsnotify_detach_mark(fsn_mark);
374 mutex_unlock(&dnotify_group->mark_mutex);
376 fsnotify_free_mark(fsn_mark);
377 fsnotify_put_mark(fsn_mark);
380 fsnotify_put_mark(new_fsn_mark);
382 kmem_cache_free(dnotify_struct_cache, dn);
386 static int __init dnotify_init(void)
388 dnotify_struct_cache = KMEM_CACHE(dnotify_struct,
389 SLAB_PANIC|SLAB_ACCOUNT);
390 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC|SLAB_ACCOUNT);
392 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
393 if (IS_ERR(dnotify_group))
394 panic("unable to allocate fsnotify group for dnotify\n");
398 module_init(dnotify_init)