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 inode *inode,
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, u32 cookie)
90 : : {
91 : : struct dnotify_mark *dn_mark;
92 : : struct dnotify_struct *dn;
93 : : struct dnotify_struct **prev;
94 : : struct fown_struct *fown;
95 : 0 : __u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
96 : :
97 : : /* not a dir, dnotify doesn't care */
98 [ # # ]: 0 : if (!S_ISDIR(inode->i_mode))
99 : : return 0;
100 : :
101 [ # # ]: 0 : BUG_ON(vfsmount_mark);
102 : :
103 : : dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
104 : :
105 : : spin_lock(&inode_mark->lock);
106 : 0 : prev = &dn_mark->dn;
107 [ # # ]: 0 : while ((dn = *prev) != NULL) {
108 [ # # ]: 0 : if ((dn->dn_mask & test_mask) == 0) {
109 : 0 : prev = &dn->dn_next;
110 : 0 : continue;
111 : : }
112 : 0 : fown = &dn->dn_filp->f_owner;
113 : 0 : send_sigio(fown, dn->dn_fd, POLL_MSG);
114 [ # # ]: 0 : if (dn->dn_mask & FS_DN_MULTISHOT)
115 : 0 : prev = &dn->dn_next;
116 : : else {
117 : 0 : *prev = dn->dn_next;
118 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
119 : 0 : dnotify_recalc_inode_mask(inode_mark);
120 : : }
121 : : }
122 : :
123 : : spin_unlock(&inode_mark->lock);
124 : :
125 : 0 : return 0;
126 : : }
127 : :
128 : 0 : static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
129 : : {
130 : : struct dnotify_mark *dn_mark = container_of(fsn_mark,
131 : : struct dnotify_mark,
132 : : fsn_mark);
133 : :
134 [ # # ]: 0 : BUG_ON(dn_mark->dn);
135 : :
136 : 0 : kmem_cache_free(dnotify_mark_cache, dn_mark);
137 : 0 : }
138 : :
139 : : static struct fsnotify_ops dnotify_fsnotify_ops = {
140 : : .handle_event = dnotify_handle_event,
141 : : };
142 : :
143 : : /*
144 : : * Called every time a file is closed. Looks first for a dnotify mark on the
145 : : * inode. If one is found run all of the ->dn structures attached to that
146 : : * mark for one relevant to this process closing the file and remove that
147 : : * dnotify_struct. If that was the last dnotify_struct also remove the
148 : : * fsnotify_mark.
149 : : */
150 : 0 : void dnotify_flush(struct file *filp, fl_owner_t id)
151 : : {
152 : : struct fsnotify_mark *fsn_mark;
153 : : struct dnotify_mark *dn_mark;
154 : : struct dnotify_struct *dn;
155 : : struct dnotify_struct **prev;
156 : : struct inode *inode;
157 : :
158 : : inode = file_inode(filp);
159 [ + + ]: 9571523 : if (!S_ISDIR(inode->i_mode))
160 : : return;
161 : :
162 : 37462 : fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
163 [ - + ]: 37463 : if (!fsn_mark)
164 : : return;
165 : : dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
166 : :
167 : 0 : mutex_lock(&dnotify_group->mark_mutex);
168 : :
169 : : spin_lock(&fsn_mark->lock);
170 : 0 : prev = &dn_mark->dn;
171 [ # # ]: 0 : while ((dn = *prev) != NULL) {
172 [ # # ][ # # ]: 0 : if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
173 : 0 : *prev = dn->dn_next;
174 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
175 : 0 : dnotify_recalc_inode_mask(fsn_mark);
176 : 0 : break;
177 : : }
178 : 0 : prev = &dn->dn_next;
179 : : }
180 : :
181 : : spin_unlock(&fsn_mark->lock);
182 : :
183 : : /* nothing else could have found us thanks to the dnotify_groups
184 : : mark_mutex */
185 [ # # ]: 0 : if (dn_mark->dn == NULL)
186 : 0 : fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
187 : :
188 : 0 : mutex_unlock(&dnotify_group->mark_mutex);
189 : :
190 : 0 : fsnotify_put_mark(fsn_mark);
191 : : }
192 : :
193 : : /* this conversion is done only at watch creation */
194 : 0 : static __u32 convert_arg(unsigned long arg)
195 : : {
196 : : __u32 new_mask = FS_EVENT_ON_CHILD;
197 : :
198 [ # # ]: 0 : if (arg & DN_MULTISHOT)
199 : : new_mask |= FS_DN_MULTISHOT;
200 [ # # ]: 0 : if (arg & DN_DELETE)
201 : 0 : new_mask |= (FS_DELETE | FS_MOVED_FROM);
202 [ # # ]: 0 : if (arg & DN_MODIFY)
203 : 0 : new_mask |= FS_MODIFY;
204 [ # # ]: 0 : if (arg & DN_ACCESS)
205 : 0 : new_mask |= FS_ACCESS;
206 [ # # ]: 0 : if (arg & DN_ATTRIB)
207 : 0 : new_mask |= FS_ATTRIB;
208 [ # # ]: 0 : if (arg & DN_RENAME)
209 : 0 : new_mask |= FS_DN_RENAME;
210 [ # # ]: 0 : if (arg & DN_CREATE)
211 : 0 : new_mask |= (FS_CREATE | FS_MOVED_TO);
212 : :
213 : 0 : return new_mask;
214 : : }
215 : :
216 : : /*
217 : : * If multiple processes watch the same inode with dnotify there is only one
218 : : * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
219 : : * onto that mark. This function either attaches the new dnotify_struct onto
220 : : * that list, or it |= the mask onto an existing dnofiy_struct.
221 : : */
222 : : static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
223 : : fl_owner_t id, int fd, struct file *filp, __u32 mask)
224 : : {
225 : : struct dnotify_struct *odn;
226 : :
227 : 0 : odn = dn_mark->dn;
228 [ # # ]: 0 : while (odn != NULL) {
229 : : /* adding more events to existing dnofiy_struct? */
230 [ # # ][ # # ]: 0 : if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
231 : 0 : odn->dn_fd = fd;
232 : 0 : odn->dn_mask |= mask;
233 : : return -EEXIST;
234 : : }
235 : 0 : odn = odn->dn_next;
236 : : }
237 : :
238 : 0 : dn->dn_mask = mask;
239 : 0 : dn->dn_fd = fd;
240 : 0 : dn->dn_filp = filp;
241 : 0 : dn->dn_owner = id;
242 : 0 : dn->dn_next = dn_mark->dn;
243 : 0 : dn_mark->dn = dn;
244 : :
245 : : return 0;
246 : : }
247 : :
248 : : /*
249 : : * When a process calls fcntl to attach a dnotify watch to a directory it ends
250 : : * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
251 : : * attached to the fsnotify_mark.
252 : : */
253 : 0 : int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
254 : : {
255 : : struct dnotify_mark *new_dn_mark, *dn_mark;
256 : : struct fsnotify_mark *new_fsn_mark, *fsn_mark;
257 : : struct dnotify_struct *dn;
258 : : struct inode *inode;
259 : 0 : fl_owner_t id = current->files;
260 : : struct file *f;
261 : : int destroy = 0, error = 0;
262 : : __u32 mask;
263 : :
264 : : /* we use these to tell if we need to kfree */
265 : : new_fsn_mark = NULL;
266 : : dn = NULL;
267 : :
268 [ # # ]: 0 : if (!dir_notify_enable) {
269 : : error = -EINVAL;
270 : : goto out_err;
271 : : }
272 : :
273 : : /* a 0 mask means we are explicitly removing the watch */
274 [ # # ]: 0 : if ((arg & ~DN_MULTISHOT) == 0) {
275 : 0 : dnotify_flush(filp, id);
276 : : error = 0;
277 : 0 : goto out_err;
278 : : }
279 : :
280 : : /* dnotify only works on directories */
281 : : inode = file_inode(filp);
282 [ # # ]: 0 : if (!S_ISDIR(inode->i_mode)) {
283 : : error = -ENOTDIR;
284 : : goto out_err;
285 : : }
286 : :
287 : : /* expect most fcntl to add new rather than augment old */
288 : 0 : dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
289 [ # # ]: 0 : if (!dn) {
290 : : error = -ENOMEM;
291 : : goto out_err;
292 : : }
293 : :
294 : : /* new fsnotify mark, we expect most fcntl calls to add a new mark */
295 : 0 : new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
296 [ # # ]: 0 : if (!new_dn_mark) {
297 : : error = -ENOMEM;
298 : : goto out_err;
299 : : }
300 : :
301 : : /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
302 : 0 : mask = convert_arg(arg);
303 : :
304 : : /* set up the new_fsn_mark and new_dn_mark */
305 : 0 : new_fsn_mark = &new_dn_mark->fsn_mark;
306 : 0 : fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
307 : 0 : new_fsn_mark->mask = mask;
308 : 0 : new_dn_mark->dn = NULL;
309 : :
310 : : /* this is needed to prevent the fcntl/close race described below */
311 : 0 : mutex_lock(&dnotify_group->mark_mutex);
312 : :
313 : : /* add the new_fsn_mark or find an old one. */
314 : 0 : fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
315 [ # # ]: 0 : if (fsn_mark) {
316 : : dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
317 : : spin_lock(&fsn_mark->lock);
318 : : } else {
319 : 0 : fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode,
320 : : NULL, 0);
321 : : spin_lock(&new_fsn_mark->lock);
322 : : fsn_mark = new_fsn_mark;
323 : : dn_mark = new_dn_mark;
324 : : /* we used new_fsn_mark, so don't free it */
325 : : new_fsn_mark = NULL;
326 : : }
327 : :
328 : : rcu_read_lock();
329 : 0 : f = fcheck(fd);
330 : : rcu_read_unlock();
331 : :
332 : : /* if (f != filp) means that we lost a race and another task/thread
333 : : * actually closed the fd we are still playing with before we grabbed
334 : : * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
335 : : * fd is the only time we clean up the marks we need to get our mark
336 : : * off the list. */
337 [ # # ]: 0 : if (f != filp) {
338 : : /* if we added ourselves, shoot ourselves, it's possible that
339 : : * the flush actually did shoot this fsn_mark. That's fine too
340 : : * since multiple calls to destroy_mark is perfectly safe, if
341 : : * we found a dn_mark already attached to the inode, just sod
342 : : * off silently as the flush at close time dealt with it.
343 : : */
344 [ # # ]: 0 : if (dn_mark == new_dn_mark)
345 : : destroy = 1;
346 : : goto out;
347 : : }
348 : :
349 : 0 : error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
350 [ # # ]: 0 : if (error) {
351 : : /* if we added, we must shoot */
352 [ # # ]: 0 : if (dn_mark == new_dn_mark)
353 : : destroy = 1;
354 : : goto out;
355 : : }
356 : :
357 : : error = attach_dn(dn, dn_mark, id, fd, filp, mask);
358 : : /* !error means that we attached the dn to the dn_mark, so don't free it */
359 [ # # ]: 0 : if (!error)
360 : : dn = NULL;
361 : : /* -EEXIST means that we didn't add this new dn and used an old one.
362 : : * that isn't an error (and the unused dn should be freed) */
363 [ # # ]: 0 : else if (error == -EEXIST)
364 : : error = 0;
365 : :
366 : 0 : dnotify_recalc_inode_mask(fsn_mark);
367 : : out:
368 : : spin_unlock(&fsn_mark->lock);
369 : :
370 [ # # ]: 0 : if (destroy)
371 : 0 : fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
372 : :
373 : 0 : mutex_unlock(&dnotify_group->mark_mutex);
374 : 0 : fsnotify_put_mark(fsn_mark);
375 : : out_err:
376 [ # # ]: 0 : if (new_fsn_mark)
377 : 0 : fsnotify_put_mark(new_fsn_mark);
378 [ # # ]: 0 : if (dn)
379 : 0 : kmem_cache_free(dnotify_struct_cache, dn);
380 : 0 : return error;
381 : : }
382 : :
383 : 0 : static int __init dnotify_init(void)
384 : : {
385 : 0 : dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
386 : 0 : dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
387 : :
388 : 0 : dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
389 [ # # ]: 0 : if (IS_ERR(dnotify_group))
390 : 0 : panic("unable to allocate fsnotify group for dnotify\n");
391 : 0 : return 0;
392 : : }
393 : :
394 : : module_init(dnotify_init)
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