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;
36 * dnotify will attach one of these to each inode (i_fsnotify_marks) which
37 * is being watched by dnotify. If multiple userspace applications are watching
38 * the same directory with dnotify their information is chained in dn
41 struct fsnotify_mark fsn_mark;
42 struct dnotify_struct *dn;
46 * When a process starts or stops watching an inode the set of events which
47 * dnotify cares about for that inode may change. This function runs the
48 * list of everything receiving dnotify events about this directory and calculates
49 * the set of all those events. After it updates what dnotify is interested in
50 * it calls the fsnotify function so it can update the set of all events relevant
53 static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
55 __u32 new_mask, old_mask;
56 struct dnotify_struct *dn;
57 struct dnotify_mark *dn_mark = container_of(fsn_mark,
61 assert_spin_locked(&fsn_mark->lock);
63 old_mask = fsn_mark->mask;
65 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
66 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
67 fsnotify_set_mark_mask_locked(fsn_mark, new_mask);
69 if (old_mask == new_mask)
72 if (fsn_mark->i.inode)
73 fsnotify_recalc_inode_mask(fsn_mark->i.inode);
77 * Mains fsnotify call where events are delivered to dnotify.
78 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
79 * on that mark and determine which of them has expressed interest in receiving
80 * events of this type. When found send the correct process and signal and
81 * destroy the dnotify struct if it was not registered to receive multiple
84 static int dnotify_handle_event(struct fsnotify_group *group,
86 struct fsnotify_mark *inode_mark,
87 struct fsnotify_mark *vfsmount_mark,
88 u32 mask, void *data, int data_type,
89 const unsigned char *file_name)
91 struct dnotify_mark *dn_mark;
92 struct dnotify_struct *dn;
93 struct dnotify_struct **prev;
94 struct fown_struct *fown;
95 __u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
97 /* not a dir, dnotify doesn't care */
98 if (!S_ISDIR(inode->i_mode))
101 BUG_ON(vfsmount_mark);
103 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
105 spin_lock(&inode_mark->lock);
107 while ((dn = *prev) != NULL) {
108 if ((dn->dn_mask & test_mask) == 0) {
112 fown = &dn->dn_filp->f_owner;
113 send_sigio(fown, dn->dn_fd, POLL_MSG);
114 if (dn->dn_mask & FS_DN_MULTISHOT)
118 kmem_cache_free(dnotify_struct_cache, dn);
119 dnotify_recalc_inode_mask(inode_mark);
123 spin_unlock(&inode_mark->lock);
128 static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
130 struct dnotify_mark *dn_mark = container_of(fsn_mark,
136 kmem_cache_free(dnotify_mark_cache, dn_mark);
139 static struct fsnotify_ops dnotify_fsnotify_ops = {
140 .handle_event = dnotify_handle_event,
141 .free_group_priv = NULL,
142 .freeing_mark = NULL,
147 * Called every time a file is closed. Looks first for a dnotify mark on the
148 * inode. If one is found run all of the ->dn structures attached to that
149 * mark for one relevant to this process closing the file and remove that
150 * dnotify_struct. If that was the last dnotify_struct also remove the
153 void dnotify_flush(struct file *filp, fl_owner_t id)
155 struct fsnotify_mark *fsn_mark;
156 struct dnotify_mark *dn_mark;
157 struct dnotify_struct *dn;
158 struct dnotify_struct **prev;
161 inode = file_inode(filp);
162 if (!S_ISDIR(inode->i_mode))
165 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
168 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
170 mutex_lock(&dnotify_group->mark_mutex);
172 spin_lock(&fsn_mark->lock);
174 while ((dn = *prev) != NULL) {
175 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
177 kmem_cache_free(dnotify_struct_cache, dn);
178 dnotify_recalc_inode_mask(fsn_mark);
184 spin_unlock(&fsn_mark->lock);
186 /* nothing else could have found us thanks to the dnotify_groups
188 if (dn_mark->dn == NULL)
189 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
191 mutex_unlock(&dnotify_group->mark_mutex);
193 fsnotify_put_mark(fsn_mark);
196 /* this conversion is done only at watch creation */
197 static __u32 convert_arg(unsigned long arg)
199 __u32 new_mask = FS_EVENT_ON_CHILD;
201 if (arg & DN_MULTISHOT)
202 new_mask |= FS_DN_MULTISHOT;
204 new_mask |= (FS_DELETE | FS_MOVED_FROM);
206 new_mask |= FS_MODIFY;
208 new_mask |= FS_ACCESS;
210 new_mask |= FS_ATTRIB;
212 new_mask |= FS_DN_RENAME;
214 new_mask |= (FS_CREATE | FS_MOVED_TO);
220 * If multiple processes watch the same inode with dnotify there is only one
221 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
222 * onto that mark. This function either attaches the new dnotify_struct onto
223 * that list, or it |= the mask onto an existing dnofiy_struct.
225 static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
226 fl_owner_t id, int fd, struct file *filp, __u32 mask)
228 struct dnotify_struct *odn;
231 while (odn != NULL) {
232 /* adding more events to existing dnofiy_struct? */
233 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
235 odn->dn_mask |= mask;
245 dn->dn_next = dn_mark->dn;
252 * When a process calls fcntl to attach a dnotify watch to a directory it ends
253 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
254 * attached to the fsnotify_mark.
256 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
258 struct dnotify_mark *new_dn_mark, *dn_mark;
259 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
260 struct dnotify_struct *dn;
262 fl_owner_t id = current->files;
264 int destroy = 0, error = 0;
267 /* we use these to tell if we need to kfree */
271 if (!dir_notify_enable) {
276 /* a 0 mask means we are explicitly removing the watch */
277 if ((arg & ~DN_MULTISHOT) == 0) {
278 dnotify_flush(filp, id);
283 /* dnotify only works on directories */
284 inode = file_inode(filp);
285 if (!S_ISDIR(inode->i_mode)) {
290 /* expect most fcntl to add new rather than augment old */
291 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
297 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
298 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
304 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
305 mask = convert_arg(arg);
307 /* set up the new_fsn_mark and new_dn_mark */
308 new_fsn_mark = &new_dn_mark->fsn_mark;
309 fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
310 new_fsn_mark->mask = mask;
311 new_dn_mark->dn = NULL;
313 /* this is needed to prevent the fcntl/close race described below */
314 mutex_lock(&dnotify_group->mark_mutex);
316 /* add the new_fsn_mark or find an old one. */
317 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
319 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
320 spin_lock(&fsn_mark->lock);
322 fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode,
324 spin_lock(&new_fsn_mark->lock);
325 fsn_mark = new_fsn_mark;
326 dn_mark = new_dn_mark;
327 /* we used new_fsn_mark, so don't free it */
335 /* if (f != filp) means that we lost a race and another task/thread
336 * actually closed the fd we are still playing with before we grabbed
337 * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
338 * fd is the only time we clean up the marks we need to get our mark
341 /* if we added ourselves, shoot ourselves, it's possible that
342 * the flush actually did shoot this fsn_mark. That's fine too
343 * since multiple calls to destroy_mark is perfectly safe, if
344 * we found a dn_mark already attached to the inode, just sod
345 * off silently as the flush at close time dealt with it.
347 if (dn_mark == new_dn_mark)
352 error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
354 /* if we added, we must shoot */
355 if (dn_mark == new_dn_mark)
360 error = attach_dn(dn, dn_mark, id, fd, filp, mask);
361 /* !error means that we attached the dn to the dn_mark, so don't free it */
364 /* -EEXIST means that we didn't add this new dn and used an old one.
365 * that isn't an error (and the unused dn should be freed) */
366 else if (error == -EEXIST)
369 dnotify_recalc_inode_mask(fsn_mark);
371 spin_unlock(&fsn_mark->lock);
374 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
376 mutex_unlock(&dnotify_group->mark_mutex);
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, SLAB_PANIC);
389 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
391 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
392 if (IS_ERR(dnotify_group))
393 panic("unable to allocate fsnotify group for dnotify\n");
397 module_init(dnotify_init)