Branch data Line data Source code
1 : : /*
2 : : * Directory notifications for Linux.
3 : : *
4 : : * Copyright (C) 2000,2001,2002 Stephen Rothwell
5 : : *
6 : : * Copyright (C) 2009 Eric Paris <Red Hat Inc>
7 : : * dnotify was largly rewritten to use the new fsnotify infrastructure
8 : : *
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
12 : : * later version.
13 : : *
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.
18 : : */
19 : : #include <linux/fs.h>
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>
28 : :
29 : : int dir_notify_enable __read_mostly = 1;
30 : :
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 : :
35 : : /*
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
39 : : */
40 : : struct dnotify_mark {
41 : : struct fsnotify_mark fsn_mark;
42 : : struct dnotify_struct *dn;
43 : : };
44 : :
45 : : /*
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
51 : : * to this inode.
52 : : */
53 : 0 : static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
54 : : {
55 : : __u32 new_mask, old_mask;
56 : : struct dnotify_struct *dn;
57 : : struct dnotify_mark *dn_mark = container_of(fsn_mark,
58 : : struct dnotify_mark,
59 : : fsn_mark);
60 : :
61 [ # # ]: 0 : assert_spin_locked(&fsn_mark->lock);
62 : :
63 : 0 : old_mask = fsn_mark->mask;
64 : : new_mask = 0;
65 [ # # ]: 0 : for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
66 : 0 : new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
67 : 0 : fsnotify_set_mark_mask_locked(fsn_mark, new_mask);
68 : :
69 [ # # ]: 0 : if (old_mask == new_mask)
70 : 0 : return;
71 : :
72 [ # # ]: 0 : if (fsn_mark->i.inode)
73 : 0 : fsnotify_recalc_inode_mask(fsn_mark->i.inode);
74 : : }
75 : :
76 : : /*
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
82 : : * events.
83 : : */
84 : 0 : static int dnotify_handle_event(struct fsnotify_group *group,
85 : : struct fsnotify_mark *inode_mark,
86 : : struct fsnotify_mark *vfsmount_mark,
87 : : struct fsnotify_event *event)
88 : : {
89 : : struct dnotify_mark *dn_mark;
90 : : struct inode *to_tell;
91 : : struct dnotify_struct *dn;
92 : : struct dnotify_struct **prev;
93 : : struct fown_struct *fown;
94 : 0 : __u32 test_mask = event->mask & ~FS_EVENT_ON_CHILD;
95 : :
96 [ # # ]: 0 : BUG_ON(vfsmount_mark);
97 : :
98 : : to_tell = event->to_tell;
99 : :
100 : : dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
101 : :
102 : : spin_lock(&inode_mark->lock);
103 : 0 : prev = &dn_mark->dn;
104 [ # # ]: 0 : while ((dn = *prev) != NULL) {
105 [ # # ]: 0 : if ((dn->dn_mask & test_mask) == 0) {
106 : 0 : prev = &dn->dn_next;
107 : 0 : continue;
108 : : }
109 : 0 : fown = &dn->dn_filp->f_owner;
110 : 0 : send_sigio(fown, dn->dn_fd, POLL_MSG);
111 [ # # ]: 0 : if (dn->dn_mask & FS_DN_MULTISHOT)
112 : 0 : prev = &dn->dn_next;
113 : : else {
114 : 0 : *prev = dn->dn_next;
115 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
116 : 0 : dnotify_recalc_inode_mask(inode_mark);
117 : : }
118 : : }
119 : :
120 : : spin_unlock(&inode_mark->lock);
121 : :
122 : 0 : return 0;
123 : : }
124 : :
125 : : /*
126 : : * Given an inode and mask determine if dnotify would be interested in sending
127 : : * userspace notification for that pair.
128 : : */
129 : 0 : static bool dnotify_should_send_event(struct fsnotify_group *group,
130 : : struct inode *inode,
131 : : struct fsnotify_mark *inode_mark,
132 : : struct fsnotify_mark *vfsmount_mark,
133 : : __u32 mask, void *data, int data_type)
134 : : {
135 : : /* not a dir, dnotify doesn't care */
136 [ # # ]: 0 : if (!S_ISDIR(inode->i_mode))
137 : : return false;
138 : :
139 : 0 : return true;
140 : : }
141 : :
142 : 0 : static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
143 : : {
144 : : struct dnotify_mark *dn_mark = container_of(fsn_mark,
145 : : struct dnotify_mark,
146 : : fsn_mark);
147 : :
148 [ # # ]: 0 : BUG_ON(dn_mark->dn);
149 : :
150 : 0 : kmem_cache_free(dnotify_mark_cache, dn_mark);
151 : 0 : }
152 : :
153 : : static struct fsnotify_ops dnotify_fsnotify_ops = {
154 : : .handle_event = dnotify_handle_event,
155 : : .should_send_event = dnotify_should_send_event,
156 : : .free_group_priv = NULL,
157 : : .freeing_mark = NULL,
158 : : .free_event_priv = NULL,
159 : : };
160 : :
161 : : /*
162 : : * Called every time a file is closed. Looks first for a dnotify mark on the
163 : : * inode. If one is found run all of the ->dn structures attached to that
164 : : * mark for one relevant to this process closing the file and remove that
165 : : * dnotify_struct. If that was the last dnotify_struct also remove the
166 : : * fsnotify_mark.
167 : : */
168 : 0 : void dnotify_flush(struct file *filp, fl_owner_t id)
169 : : {
170 : : struct fsnotify_mark *fsn_mark;
171 : : struct dnotify_mark *dn_mark;
172 : : struct dnotify_struct *dn;
173 : : struct dnotify_struct **prev;
174 : : struct inode *inode;
175 : :
176 : : inode = file_inode(filp);
177 [ + + ]: 10901224 : if (!S_ISDIR(inode->i_mode))
178 : : return;
179 : :
180 : 75377 : fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
181 [ - + ]: 75380 : if (!fsn_mark)
182 : : return;
183 : : dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
184 : :
185 : 0 : mutex_lock(&dnotify_group->mark_mutex);
186 : :
187 : : spin_lock(&fsn_mark->lock);
188 : 0 : prev = &dn_mark->dn;
189 [ # # ]: 0 : while ((dn = *prev) != NULL) {
190 [ # # ][ # # ]: 0 : if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
191 : 0 : *prev = dn->dn_next;
192 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
193 : 0 : dnotify_recalc_inode_mask(fsn_mark);
194 : 0 : break;
195 : : }
196 : 0 : prev = &dn->dn_next;
197 : : }
198 : :
199 : : spin_unlock(&fsn_mark->lock);
200 : :
201 : : /* nothing else could have found us thanks to the dnotify_groups
202 : : mark_mutex */
203 [ # # ]: 0 : if (dn_mark->dn == NULL)
204 : 0 : fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
205 : :
206 : 0 : mutex_unlock(&dnotify_group->mark_mutex);
207 : :
208 : 0 : fsnotify_put_mark(fsn_mark);
209 : : }
210 : :
211 : : /* this conversion is done only at watch creation */
212 : 0 : static __u32 convert_arg(unsigned long arg)
213 : : {
214 : : __u32 new_mask = FS_EVENT_ON_CHILD;
215 : :
216 [ # # ]: 0 : if (arg & DN_MULTISHOT)
217 : : new_mask |= FS_DN_MULTISHOT;
218 [ # # ]: 0 : if (arg & DN_DELETE)
219 : 0 : new_mask |= (FS_DELETE | FS_MOVED_FROM);
220 [ # # ]: 0 : if (arg & DN_MODIFY)
221 : 0 : new_mask |= FS_MODIFY;
222 [ # # ]: 0 : if (arg & DN_ACCESS)
223 : 0 : new_mask |= FS_ACCESS;
224 [ # # ]: 0 : if (arg & DN_ATTRIB)
225 : 0 : new_mask |= FS_ATTRIB;
226 [ # # ]: 0 : if (arg & DN_RENAME)
227 : 0 : new_mask |= FS_DN_RENAME;
228 [ # # ]: 0 : if (arg & DN_CREATE)
229 : 0 : new_mask |= (FS_CREATE | FS_MOVED_TO);
230 : :
231 : 0 : return new_mask;
232 : : }
233 : :
234 : : /*
235 : : * If multiple processes watch the same inode with dnotify there is only one
236 : : * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
237 : : * onto that mark. This function either attaches the new dnotify_struct onto
238 : : * that list, or it |= the mask onto an existing dnofiy_struct.
239 : : */
240 : : static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
241 : : fl_owner_t id, int fd, struct file *filp, __u32 mask)
242 : : {
243 : : struct dnotify_struct *odn;
244 : :
245 : 0 : odn = dn_mark->dn;
246 [ # # ]: 0 : while (odn != NULL) {
247 : : /* adding more events to existing dnofiy_struct? */
248 [ # # ][ # # ]: 0 : if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
249 : 0 : odn->dn_fd = fd;
250 : 0 : odn->dn_mask |= mask;
251 : : return -EEXIST;
252 : : }
253 : 0 : odn = odn->dn_next;
254 : : }
255 : :
256 : 0 : dn->dn_mask = mask;
257 : 0 : dn->dn_fd = fd;
258 : 0 : dn->dn_filp = filp;
259 : 0 : dn->dn_owner = id;
260 : 0 : dn->dn_next = dn_mark->dn;
261 : 0 : dn_mark->dn = dn;
262 : :
263 : : return 0;
264 : : }
265 : :
266 : : /*
267 : : * When a process calls fcntl to attach a dnotify watch to a directory it ends
268 : : * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
269 : : * attached to the fsnotify_mark.
270 : : */
271 : 0 : int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
272 : : {
273 : : struct dnotify_mark *new_dn_mark, *dn_mark;
274 : : struct fsnotify_mark *new_fsn_mark, *fsn_mark;
275 : : struct dnotify_struct *dn;
276 : : struct inode *inode;
277 : 0 : fl_owner_t id = current->files;
278 : : struct file *f;
279 : : int destroy = 0, error = 0;
280 : : __u32 mask;
281 : :
282 : : /* we use these to tell if we need to kfree */
283 : : new_fsn_mark = NULL;
284 : : dn = NULL;
285 : :
286 [ # # ]: 0 : if (!dir_notify_enable) {
287 : : error = -EINVAL;
288 : : goto out_err;
289 : : }
290 : :
291 : : /* a 0 mask means we are explicitly removing the watch */
292 [ # # ]: 0 : if ((arg & ~DN_MULTISHOT) == 0) {
293 : 0 : dnotify_flush(filp, id);
294 : : error = 0;
295 : 0 : goto out_err;
296 : : }
297 : :
298 : : /* dnotify only works on directories */
299 : : inode = file_inode(filp);
300 [ # # ]: 0 : if (!S_ISDIR(inode->i_mode)) {
301 : : error = -ENOTDIR;
302 : : goto out_err;
303 : : }
304 : :
305 : : /* expect most fcntl to add new rather than augment old */
306 : 0 : dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
307 [ # # ]: 0 : if (!dn) {
308 : : error = -ENOMEM;
309 : : goto out_err;
310 : : }
311 : :
312 : : /* new fsnotify mark, we expect most fcntl calls to add a new mark */
313 : 0 : new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
314 [ # # ]: 0 : if (!new_dn_mark) {
315 : : error = -ENOMEM;
316 : : goto out_err;
317 : : }
318 : :
319 : : /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
320 : 0 : mask = convert_arg(arg);
321 : :
322 : : /* set up the new_fsn_mark and new_dn_mark */
323 : 0 : new_fsn_mark = &new_dn_mark->fsn_mark;
324 : 0 : fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
325 : 0 : new_fsn_mark->mask = mask;
326 : 0 : new_dn_mark->dn = NULL;
327 : :
328 : : /* this is needed to prevent the fcntl/close race described below */
329 : 0 : mutex_lock(&dnotify_group->mark_mutex);
330 : :
331 : : /* add the new_fsn_mark or find an old one. */
332 : 0 : fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
333 [ # # ]: 0 : if (fsn_mark) {
334 : : dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
335 : : spin_lock(&fsn_mark->lock);
336 : : } else {
337 : 0 : fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode,
338 : : NULL, 0);
339 : : spin_lock(&new_fsn_mark->lock);
340 : : fsn_mark = new_fsn_mark;
341 : : dn_mark = new_dn_mark;
342 : : /* we used new_fsn_mark, so don't free it */
343 : : new_fsn_mark = NULL;
344 : : }
345 : :
346 : : rcu_read_lock();
347 : 0 : f = fcheck(fd);
348 : : rcu_read_unlock();
349 : :
350 : : /* if (f != filp) means that we lost a race and another task/thread
351 : : * actually closed the fd we are still playing with before we grabbed
352 : : * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
353 : : * fd is the only time we clean up the marks we need to get our mark
354 : : * off the list. */
355 [ # # ]: 0 : if (f != filp) {
356 : : /* if we added ourselves, shoot ourselves, it's possible that
357 : : * the flush actually did shoot this fsn_mark. That's fine too
358 : : * since multiple calls to destroy_mark is perfectly safe, if
359 : : * we found a dn_mark already attached to the inode, just sod
360 : : * off silently as the flush at close time dealt with it.
361 : : */
362 [ # # ]: 0 : if (dn_mark == new_dn_mark)
363 : : destroy = 1;
364 : : goto out;
365 : : }
366 : :
367 : 0 : error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
368 [ # # ]: 0 : if (error) {
369 : : /* if we added, we must shoot */
370 [ # # ]: 0 : if (dn_mark == new_dn_mark)
371 : : destroy = 1;
372 : : goto out;
373 : : }
374 : :
375 : : error = attach_dn(dn, dn_mark, id, fd, filp, mask);
376 : : /* !error means that we attached the dn to the dn_mark, so don't free it */
377 [ # # ]: 0 : if (!error)
378 : : dn = NULL;
379 : : /* -EEXIST means that we didn't add this new dn and used an old one.
380 : : * that isn't an error (and the unused dn should be freed) */
381 [ # # ]: 0 : else if (error == -EEXIST)
382 : : error = 0;
383 : :
384 : 0 : dnotify_recalc_inode_mask(fsn_mark);
385 : : out:
386 : : spin_unlock(&fsn_mark->lock);
387 : :
388 [ # # ]: 0 : if (destroy)
389 : 0 : fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
390 : :
391 : 0 : mutex_unlock(&dnotify_group->mark_mutex);
392 : 0 : fsnotify_put_mark(fsn_mark);
393 : : out_err:
394 [ # # ]: 0 : if (new_fsn_mark)
395 : 0 : fsnotify_put_mark(new_fsn_mark);
396 [ # # ]: 0 : if (dn)
397 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
398 : 0 : return error;
399 : : }
400 : :
401 : 0 : static int __init dnotify_init(void)
402 : : {
403 : 0 : dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
404 : 0 : dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
405 : :
406 : 0 : dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
407 [ # # ]: 0 : if (IS_ERR(dnotify_group))
408 : 0 : panic("unable to allocate fsnotify group for dnotify\n");
409 : 0 : return 0;
410 : : }
411 : :
412 : : module_init(dnotify_init)
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