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/dnotify.h>
23 #include <linux/init.h>
24 #include <linux/spinlock.h>
25 #include <linux/slab.h>
26 #include <linux/fdtable.h>
27 #include <linux/fsnotify_backend.h>
29 int dir_notify_enable __read_mostly = 1;
31 static struct kmem_cache *dnotify_struct_cache __read_mostly;
32 static struct kmem_cache *dnotify_mark_cache __read_mostly;
33 static struct fsnotify_group *dnotify_group __read_mostly;
34 static DEFINE_MUTEX(dnotify_mark_mutex);
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)
56 __u32 new_mask, old_mask;
57 struct dnotify_struct *dn;
58 struct dnotify_mark *dn_mark = container_of(fsn_mark,
62 assert_spin_locked(&fsn_mark->lock);
64 old_mask = fsn_mark->mask;
66 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
67 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
68 fsnotify_set_mark_mask_locked(fsn_mark, new_mask);
70 if (old_mask == new_mask)
73 if (fsn_mark->i.inode)
74 fsnotify_recalc_inode_mask(fsn_mark->i.inode);
78 * Mains fsnotify call where events are delivered to dnotify.
79 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
80 * on that mark and determine which of them has expressed interest in receiving
81 * events of this type. When found send the correct process and signal and
82 * destroy the dnotify struct if it was not registered to receive multiple
85 static int dnotify_handle_event(struct fsnotify_group *group,
86 struct fsnotify_mark *mark,
87 struct fsnotify_event *event)
89 struct fsnotify_mark *fsn_mark = NULL;
90 struct dnotify_mark *dn_mark;
91 struct inode *to_tell;
92 struct dnotify_struct *dn;
93 struct dnotify_struct **prev;
94 struct fown_struct *fown;
95 __u32 test_mask = event->mask & ~FS_EVENT_ON_CHILD;
97 to_tell = event->to_tell;
99 fsn_mark = fsnotify_find_inode_mark(group, to_tell);
100 if (unlikely(!fsn_mark))
102 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
104 spin_lock(&fsn_mark->lock);
106 while ((dn = *prev) != NULL) {
107 if ((dn->dn_mask & test_mask) == 0) {
111 fown = &dn->dn_filp->f_owner;
112 send_sigio(fown, dn->dn_fd, POLL_MSG);
113 if (dn->dn_mask & FS_DN_MULTISHOT)
117 kmem_cache_free(dnotify_struct_cache, dn);
118 dnotify_recalc_inode_mask(fsn_mark);
122 spin_unlock(&fsn_mark->lock);
123 fsnotify_put_mark(fsn_mark);
129 * Given an inode and mask determine if dnotify would be interested in sending
130 * userspace notification for that pair.
132 static bool dnotify_should_send_event(struct fsnotify_group *group,
133 struct inode *inode, struct vfsmount *mnt,
134 struct fsnotify_mark *mark, __u32 mask,
135 void *data, int data_type)
137 struct fsnotify_mark *fsn_mark;
140 /* !dir_notify_enable should never get here, don't waste time checking
141 if (!dir_notify_enable)
144 /* not a dir, dnotify doesn't care */
145 if (!S_ISDIR(inode->i_mode))
148 fsn_mark = fsnotify_find_inode_mark(group, inode);
152 mask = (mask & ~FS_EVENT_ON_CHILD);
153 send = (mask & fsn_mark->mask);
155 fsnotify_put_mark(fsn_mark); /* matches fsnotify_find_inode_mark */
160 static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
162 struct dnotify_mark *dn_mark = container_of(fsn_mark,
168 kmem_cache_free(dnotify_mark_cache, dn_mark);
171 static struct fsnotify_ops dnotify_fsnotify_ops = {
172 .handle_event = dnotify_handle_event,
173 .should_send_event = dnotify_should_send_event,
174 .free_group_priv = NULL,
175 .freeing_mark = NULL,
176 .free_event_priv = NULL,
180 * Called every time a file is closed. Looks first for a dnotify mark on the
181 * inode. If one is found run all of the ->dn structures attached to that
182 * mark for one relevant to this process closing the file and remove that
183 * dnotify_struct. If that was the last dnotify_struct also remove the
186 void dnotify_flush(struct file *filp, fl_owner_t id)
188 struct fsnotify_mark *fsn_mark;
189 struct dnotify_mark *dn_mark;
190 struct dnotify_struct *dn;
191 struct dnotify_struct **prev;
194 inode = filp->f_path.dentry->d_inode;
195 if (!S_ISDIR(inode->i_mode))
198 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
201 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
203 mutex_lock(&dnotify_mark_mutex);
205 spin_lock(&fsn_mark->lock);
207 while ((dn = *prev) != NULL) {
208 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
210 kmem_cache_free(dnotify_struct_cache, dn);
211 dnotify_recalc_inode_mask(fsn_mark);
217 spin_unlock(&fsn_mark->lock);
219 /* nothing else could have found us thanks to the dnotify_mark_mutex */
220 if (dn_mark->dn == NULL)
221 fsnotify_destroy_mark(fsn_mark);
223 fsnotify_recalc_group_mask(dnotify_group);
225 mutex_unlock(&dnotify_mark_mutex);
227 fsnotify_put_mark(fsn_mark);
230 /* this conversion is done only at watch creation */
231 static __u32 convert_arg(unsigned long arg)
233 __u32 new_mask = FS_EVENT_ON_CHILD;
235 if (arg & DN_MULTISHOT)
236 new_mask |= FS_DN_MULTISHOT;
238 new_mask |= (FS_DELETE | FS_MOVED_FROM);
240 new_mask |= FS_MODIFY;
242 new_mask |= FS_ACCESS;
244 new_mask |= FS_ATTRIB;
246 new_mask |= FS_DN_RENAME;
248 new_mask |= (FS_CREATE | FS_MOVED_TO);
254 * If multiple processes watch the same inode with dnotify there is only one
255 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
256 * onto that mark. This function either attaches the new dnotify_struct onto
257 * that list, or it |= the mask onto an existing dnofiy_struct.
259 static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
260 fl_owner_t id, int fd, struct file *filp, __u32 mask)
262 struct dnotify_struct *odn;
265 while (odn != NULL) {
266 /* adding more events to existing dnofiy_struct? */
267 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
269 odn->dn_mask |= mask;
279 dn->dn_next = dn_mark->dn;
286 * When a process calls fcntl to attach a dnotify watch to a directory it ends
287 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
288 * attached to the fsnotify_mark.
290 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
292 struct dnotify_mark *new_dn_mark, *dn_mark;
293 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
294 struct dnotify_struct *dn;
296 fl_owner_t id = current->files;
298 int destroy = 0, error = 0;
301 /* we use these to tell if we need to kfree */
305 if (!dir_notify_enable) {
310 /* a 0 mask means we are explicitly removing the watch */
311 if ((arg & ~DN_MULTISHOT) == 0) {
312 dnotify_flush(filp, id);
317 /* dnotify only works on directories */
318 inode = filp->f_path.dentry->d_inode;
319 if (!S_ISDIR(inode->i_mode)) {
324 /* expect most fcntl to add new rather than augment old */
325 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
331 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
332 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
338 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
339 mask = convert_arg(arg);
341 /* set up the new_fsn_mark and new_dn_mark */
342 new_fsn_mark = &new_dn_mark->fsn_mark;
343 fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
344 new_fsn_mark->mask = mask;
345 new_dn_mark->dn = NULL;
347 /* this is needed to prevent the fcntl/close race described below */
348 mutex_lock(&dnotify_mark_mutex);
350 /* add the new_fsn_mark or find an old one. */
351 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
353 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
354 spin_lock(&fsn_mark->lock);
356 fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, NULL, 0);
357 spin_lock(&new_fsn_mark->lock);
358 fsn_mark = new_fsn_mark;
359 dn_mark = new_dn_mark;
360 /* we used new_fsn_mark, so don't free it */
368 /* if (f != filp) means that we lost a race and another task/thread
369 * actually closed the fd we are still playing with before we grabbed
370 * the dnotify_mark_mutex and fsn_mark->lock. Since closing the fd is the
371 * only time we clean up the marks we need to get our mark off
374 /* if we added ourselves, shoot ourselves, it's possible that
375 * the flush actually did shoot this fsn_mark. That's fine too
376 * since multiple calls to destroy_mark is perfectly safe, if
377 * we found a dn_mark already attached to the inode, just sod
378 * off silently as the flush at close time dealt with it.
380 if (dn_mark == new_dn_mark)
385 error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
387 /* if we added, we must shoot */
388 if (dn_mark == new_dn_mark)
393 error = attach_dn(dn, dn_mark, id, fd, filp, mask);
394 /* !error means that we attached the dn to the dn_mark, so don't free it */
397 /* -EEXIST means that we didn't add this new dn and used an old one.
398 * that isn't an error (and the unused dn should be freed) */
399 else if (error == -EEXIST)
402 dnotify_recalc_inode_mask(fsn_mark);
404 spin_unlock(&fsn_mark->lock);
407 fsnotify_destroy_mark(fsn_mark);
409 fsnotify_recalc_group_mask(dnotify_group);
411 mutex_unlock(&dnotify_mark_mutex);
412 fsnotify_put_mark(fsn_mark);
415 fsnotify_put_mark(new_fsn_mark);
417 kmem_cache_free(dnotify_struct_cache, dn);
421 static int __init dnotify_init(void)
423 dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
424 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
426 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
427 if (IS_ERR(dnotify_group))
428 panic("unable to allocate fsnotify group for dnotify\n");
432 module_init(dnotify_init)