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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * Directory notifications for Linux. | |
3 | * | |
4 | * Copyright (C) 2000,2001,2002 Stephen Rothwell | |
5 | * | |
3c5119c0 EP |
6 | * Copyright (C) 2009 Eric Paris <Red Hat Inc> |
7 | * dnotify was largly rewritten to use the new fsnotify infrastructure | |
8 | * | |
1da177e4 LT |
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> | |
9f3acc31 | 26 | #include <linux/fdtable.h> |
3c5119c0 | 27 | #include <linux/fsnotify_backend.h> |
1da177e4 | 28 | |
fa3536cc | 29 | int dir_notify_enable __read_mostly = 1; |
1da177e4 | 30 | |
3c5119c0 | 31 | static struct kmem_cache *dnotify_struct_cache __read_mostly; |
ef5e2b78 | 32 | static struct kmem_cache *dnotify_mark_cache __read_mostly; |
3c5119c0 EP |
33 | static struct fsnotify_group *dnotify_group __read_mostly; |
34 | static DEFINE_MUTEX(dnotify_mark_mutex); | |
35 | ||
36 | /* | |
e61ce867 | 37 | * dnotify will attach one of these to each inode (i_fsnotify_marks) which |
3c5119c0 EP |
38 | * is being watched by dnotify. If multiple userspace applications are watching |
39 | * the same directory with dnotify their information is chained in dn | |
40 | */ | |
ef5e2b78 EP |
41 | struct dnotify_mark { |
42 | struct fsnotify_mark fsn_mark; | |
3c5119c0 EP |
43 | struct dnotify_struct *dn; |
44 | }; | |
1da177e4 | 45 | |
3c5119c0 EP |
46 | /* |
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 | |
52 | * to this inode. | |
53 | */ | |
ef5e2b78 | 54 | static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) |
1da177e4 | 55 | { |
3c5119c0 | 56 | __u32 new_mask, old_mask; |
1da177e4 | 57 | struct dnotify_struct *dn; |
ef5e2b78 EP |
58 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
59 | struct dnotify_mark, | |
60 | fsn_mark); | |
3c5119c0 | 61 | |
ef5e2b78 | 62 | assert_spin_locked(&fsn_mark->lock); |
1da177e4 | 63 | |
ef5e2b78 | 64 | old_mask = fsn_mark->mask; |
1da177e4 | 65 | new_mask = 0; |
ef5e2b78 | 66 | for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) |
3c5119c0 | 67 | new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); |
90b1e7a5 | 68 | fsnotify_set_mark_mask_locked(fsn_mark, new_mask); |
3c5119c0 EP |
69 | |
70 | if (old_mask == new_mask) | |
71 | return; | |
72 | ||
ef5e2b78 EP |
73 | if (fsn_mark->i.inode) |
74 | fsnotify_recalc_inode_mask(fsn_mark->i.inode); | |
1da177e4 LT |
75 | } |
76 | ||
3c5119c0 EP |
77 | /* |
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 | |
83 | * events. | |
84 | */ | |
85 | static int dnotify_handle_event(struct fsnotify_group *group, | |
86 | struct fsnotify_event *event) | |
87 | { | |
ef5e2b78 EP |
88 | struct fsnotify_mark *fsn_mark = NULL; |
89 | struct dnotify_mark *dn_mark; | |
3c5119c0 EP |
90 | struct inode *to_tell; |
91 | struct dnotify_struct *dn; | |
92 | struct dnotify_struct **prev; | |
93 | struct fown_struct *fown; | |
94552684 | 94 | __u32 test_mask = event->mask & ~FS_EVENT_ON_CHILD; |
3c5119c0 EP |
95 | |
96 | to_tell = event->to_tell; | |
97 | ||
5444e298 | 98 | fsn_mark = fsnotify_find_inode_mark(group, to_tell); |
ef5e2b78 | 99 | if (unlikely(!fsn_mark)) |
3c5119c0 | 100 | return 0; |
ef5e2b78 | 101 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 | 102 | |
ef5e2b78 EP |
103 | spin_lock(&fsn_mark->lock); |
104 | prev = &dn_mark->dn; | |
3c5119c0 | 105 | while ((dn = *prev) != NULL) { |
94552684 | 106 | if ((dn->dn_mask & test_mask) == 0) { |
3c5119c0 EP |
107 | prev = &dn->dn_next; |
108 | continue; | |
109 | } | |
110 | fown = &dn->dn_filp->f_owner; | |
111 | send_sigio(fown, dn->dn_fd, POLL_MSG); | |
112 | if (dn->dn_mask & FS_DN_MULTISHOT) | |
113 | prev = &dn->dn_next; | |
114 | else { | |
115 | *prev = dn->dn_next; | |
116 | kmem_cache_free(dnotify_struct_cache, dn); | |
ef5e2b78 | 117 | dnotify_recalc_inode_mask(fsn_mark); |
3c5119c0 EP |
118 | } |
119 | } | |
120 | ||
ef5e2b78 EP |
121 | spin_unlock(&fsn_mark->lock); |
122 | fsnotify_put_mark(fsn_mark); | |
3c5119c0 EP |
123 | |
124 | return 0; | |
125 | } | |
126 | ||
127 | /* | |
128 | * Given an inode and mask determine if dnotify would be interested in sending | |
129 | * userspace notification for that pair. | |
130 | */ | |
131 | static bool dnotify_should_send_event(struct fsnotify_group *group, | |
3a9fb89f EP |
132 | struct inode *inode, struct vfsmount *mnt, |
133 | __u32 mask, void *data, int data_type) | |
3c5119c0 | 134 | { |
ef5e2b78 | 135 | struct fsnotify_mark *fsn_mark; |
3c5119c0 EP |
136 | bool send; |
137 | ||
138 | /* !dir_notify_enable should never get here, don't waste time checking | |
139 | if (!dir_notify_enable) | |
140 | return 0; */ | |
141 | ||
142 | /* not a dir, dnotify doesn't care */ | |
143 | if (!S_ISDIR(inode->i_mode)) | |
144 | return false; | |
145 | ||
5444e298 | 146 | fsn_mark = fsnotify_find_inode_mark(group, inode); |
ef5e2b78 | 147 | if (!fsn_mark) |
3c5119c0 EP |
148 | return false; |
149 | ||
e42e2773 | 150 | mask = (mask & ~FS_EVENT_ON_CHILD); |
ef5e2b78 | 151 | send = (mask & fsn_mark->mask); |
ce61856b | 152 | |
5444e298 | 153 | fsnotify_put_mark(fsn_mark); /* matches fsnotify_find_inode_mark */ |
3c5119c0 EP |
154 | |
155 | return send; | |
156 | } | |
157 | ||
ef5e2b78 | 158 | static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) |
3c5119c0 | 159 | { |
ef5e2b78 EP |
160 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
161 | struct dnotify_mark, | |
162 | fsn_mark); | |
3c5119c0 | 163 | |
ef5e2b78 | 164 | BUG_ON(dn_mark->dn); |
3c5119c0 | 165 | |
ef5e2b78 | 166 | kmem_cache_free(dnotify_mark_cache, dn_mark); |
3c5119c0 EP |
167 | } |
168 | ||
169 | static struct fsnotify_ops dnotify_fsnotify_ops = { | |
170 | .handle_event = dnotify_handle_event, | |
171 | .should_send_event = dnotify_should_send_event, | |
172 | .free_group_priv = NULL, | |
a092ee20 | 173 | .freeing_mark = NULL, |
e4aff117 | 174 | .free_event_priv = NULL, |
3c5119c0 EP |
175 | }; |
176 | ||
177 | /* | |
178 | * Called every time a file is closed. Looks first for a dnotify mark on the | |
e61ce867 | 179 | * inode. If one is found run all of the ->dn structures attached to that |
3c5119c0 EP |
180 | * mark for one relevant to this process closing the file and remove that |
181 | * dnotify_struct. If that was the last dnotify_struct also remove the | |
e61ce867 | 182 | * fsnotify_mark. |
3c5119c0 | 183 | */ |
1da177e4 LT |
184 | void dnotify_flush(struct file *filp, fl_owner_t id) |
185 | { | |
ef5e2b78 EP |
186 | struct fsnotify_mark *fsn_mark; |
187 | struct dnotify_mark *dn_mark; | |
1da177e4 LT |
188 | struct dnotify_struct *dn; |
189 | struct dnotify_struct **prev; | |
190 | struct inode *inode; | |
191 | ||
0f7fc9e4 | 192 | inode = filp->f_path.dentry->d_inode; |
1da177e4 LT |
193 | if (!S_ISDIR(inode->i_mode)) |
194 | return; | |
3c5119c0 | 195 | |
5444e298 | 196 | fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); |
ef5e2b78 | 197 | if (!fsn_mark) |
3c5119c0 | 198 | return; |
ef5e2b78 | 199 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 EP |
200 | |
201 | mutex_lock(&dnotify_mark_mutex); | |
202 | ||
ef5e2b78 EP |
203 | spin_lock(&fsn_mark->lock); |
204 | prev = &dn_mark->dn; | |
1da177e4 LT |
205 | while ((dn = *prev) != NULL) { |
206 | if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { | |
207 | *prev = dn->dn_next; | |
3c5119c0 | 208 | kmem_cache_free(dnotify_struct_cache, dn); |
ef5e2b78 | 209 | dnotify_recalc_inode_mask(fsn_mark); |
1da177e4 LT |
210 | break; |
211 | } | |
212 | prev = &dn->dn_next; | |
213 | } | |
3c5119c0 | 214 | |
ef5e2b78 | 215 | spin_unlock(&fsn_mark->lock); |
3c5119c0 EP |
216 | |
217 | /* nothing else could have found us thanks to the dnotify_mark_mutex */ | |
ef5e2b78 EP |
218 | if (dn_mark->dn == NULL) |
219 | fsnotify_destroy_mark(fsn_mark); | |
3c5119c0 EP |
220 | |
221 | fsnotify_recalc_group_mask(dnotify_group); | |
222 | ||
223 | mutex_unlock(&dnotify_mark_mutex); | |
224 | ||
ef5e2b78 | 225 | fsnotify_put_mark(fsn_mark); |
3c5119c0 EP |
226 | } |
227 | ||
228 | /* this conversion is done only at watch creation */ | |
229 | static __u32 convert_arg(unsigned long arg) | |
230 | { | |
231 | __u32 new_mask = FS_EVENT_ON_CHILD; | |
232 | ||
233 | if (arg & DN_MULTISHOT) | |
234 | new_mask |= FS_DN_MULTISHOT; | |
235 | if (arg & DN_DELETE) | |
236 | new_mask |= (FS_DELETE | FS_MOVED_FROM); | |
237 | if (arg & DN_MODIFY) | |
238 | new_mask |= FS_MODIFY; | |
239 | if (arg & DN_ACCESS) | |
240 | new_mask |= FS_ACCESS; | |
241 | if (arg & DN_ATTRIB) | |
242 | new_mask |= FS_ATTRIB; | |
243 | if (arg & DN_RENAME) | |
244 | new_mask |= FS_DN_RENAME; | |
245 | if (arg & DN_CREATE) | |
246 | new_mask |= (FS_CREATE | FS_MOVED_TO); | |
247 | ||
248 | return new_mask; | |
1da177e4 LT |
249 | } |
250 | ||
3c5119c0 EP |
251 | /* |
252 | * If multiple processes watch the same inode with dnotify there is only one | |
e61ce867 | 253 | * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct |
3c5119c0 EP |
254 | * onto that mark. This function either attaches the new dnotify_struct onto |
255 | * that list, or it |= the mask onto an existing dnofiy_struct. | |
256 | */ | |
ef5e2b78 | 257 | static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, |
3c5119c0 EP |
258 | fl_owner_t id, int fd, struct file *filp, __u32 mask) |
259 | { | |
260 | struct dnotify_struct *odn; | |
261 | ||
ef5e2b78 | 262 | odn = dn_mark->dn; |
3c5119c0 EP |
263 | while (odn != NULL) { |
264 | /* adding more events to existing dnofiy_struct? */ | |
265 | if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { | |
266 | odn->dn_fd = fd; | |
267 | odn->dn_mask |= mask; | |
268 | return -EEXIST; | |
269 | } | |
270 | odn = odn->dn_next; | |
271 | } | |
272 | ||
273 | dn->dn_mask = mask; | |
274 | dn->dn_fd = fd; | |
275 | dn->dn_filp = filp; | |
276 | dn->dn_owner = id; | |
ef5e2b78 EP |
277 | dn->dn_next = dn_mark->dn; |
278 | dn_mark->dn = dn; | |
3c5119c0 EP |
279 | |
280 | return 0; | |
281 | } | |
282 | ||
283 | /* | |
284 | * When a process calls fcntl to attach a dnotify watch to a directory it ends | |
285 | * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be | |
286 | * attached to the fsnotify_mark. | |
287 | */ | |
1da177e4 LT |
288 | int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) |
289 | { | |
ef5e2b78 EP |
290 | struct dnotify_mark *new_dn_mark, *dn_mark; |
291 | struct fsnotify_mark *new_fsn_mark, *fsn_mark; | |
1da177e4 | 292 | struct dnotify_struct *dn; |
1da177e4 LT |
293 | struct inode *inode; |
294 | fl_owner_t id = current->files; | |
214b7049 | 295 | struct file *f; |
3c5119c0 EP |
296 | int destroy = 0, error = 0; |
297 | __u32 mask; | |
298 | ||
299 | /* we use these to tell if we need to kfree */ | |
ef5e2b78 | 300 | new_fsn_mark = NULL; |
3c5119c0 | 301 | dn = NULL; |
1da177e4 | 302 | |
3c5119c0 EP |
303 | if (!dir_notify_enable) { |
304 | error = -EINVAL; | |
305 | goto out_err; | |
306 | } | |
307 | ||
308 | /* a 0 mask means we are explicitly removing the watch */ | |
1da177e4 LT |
309 | if ((arg & ~DN_MULTISHOT) == 0) { |
310 | dnotify_flush(filp, id); | |
3c5119c0 EP |
311 | error = 0; |
312 | goto out_err; | |
1da177e4 | 313 | } |
3c5119c0 EP |
314 | |
315 | /* dnotify only works on directories */ | |
0f7fc9e4 | 316 | inode = filp->f_path.dentry->d_inode; |
3c5119c0 EP |
317 | if (!S_ISDIR(inode->i_mode)) { |
318 | error = -ENOTDIR; | |
319 | goto out_err; | |
1da177e4 LT |
320 | } |
321 | ||
3c5119c0 EP |
322 | /* expect most fcntl to add new rather than augment old */ |
323 | dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); | |
324 | if (!dn) { | |
325 | error = -ENOMEM; | |
326 | goto out_err; | |
327 | } | |
214b7049 | 328 | |
3c5119c0 | 329 | /* new fsnotify mark, we expect most fcntl calls to add a new mark */ |
ef5e2b78 EP |
330 | new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); |
331 | if (!new_dn_mark) { | |
3c5119c0 EP |
332 | error = -ENOMEM; |
333 | goto out_err; | |
334 | } | |
1da177e4 | 335 | |
3c5119c0 EP |
336 | /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */ |
337 | mask = convert_arg(arg); | |
1da177e4 | 338 | |
ef5e2b78 EP |
339 | /* set up the new_fsn_mark and new_dn_mark */ |
340 | new_fsn_mark = &new_dn_mark->fsn_mark; | |
341 | fsnotify_init_mark(new_fsn_mark, dnotify_free_mark); | |
342 | new_fsn_mark->mask = mask; | |
343 | new_dn_mark->dn = NULL; | |
1da177e4 | 344 | |
3c5119c0 EP |
345 | /* this is needed to prevent the fcntl/close race described below */ |
346 | mutex_lock(&dnotify_mark_mutex); | |
1da177e4 | 347 | |
ef5e2b78 | 348 | /* add the new_fsn_mark or find an old one. */ |
5444e298 | 349 | fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); |
ef5e2b78 EP |
350 | if (fsn_mark) { |
351 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); | |
352 | spin_lock(&fsn_mark->lock); | |
3c5119c0 | 353 | } else { |
5444e298 | 354 | fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, NULL, 0); |
ef5e2b78 EP |
355 | spin_lock(&new_fsn_mark->lock); |
356 | fsn_mark = new_fsn_mark; | |
357 | dn_mark = new_dn_mark; | |
358 | /* we used new_fsn_mark, so don't free it */ | |
359 | new_fsn_mark = NULL; | |
3c5119c0 | 360 | } |
1da177e4 | 361 | |
3c5119c0 EP |
362 | rcu_read_lock(); |
363 | f = fcheck(fd); | |
364 | rcu_read_unlock(); | |
1da177e4 | 365 | |
3c5119c0 EP |
366 | /* if (f != filp) means that we lost a race and another task/thread |
367 | * actually closed the fd we are still playing with before we grabbed | |
ef5e2b78 | 368 | * the dnotify_mark_mutex and fsn_mark->lock. Since closing the fd is the |
e61ce867 | 369 | * only time we clean up the marks we need to get our mark off |
3c5119c0 EP |
370 | * the list. */ |
371 | if (f != filp) { | |
372 | /* if we added ourselves, shoot ourselves, it's possible that | |
ef5e2b78 | 373 | * the flush actually did shoot this fsn_mark. That's fine too |
3c5119c0 | 374 | * since multiple calls to destroy_mark is perfectly safe, if |
ef5e2b78 | 375 | * we found a dn_mark already attached to the inode, just sod |
3c5119c0 EP |
376 | * off silently as the flush at close time dealt with it. |
377 | */ | |
ef5e2b78 | 378 | if (dn_mark == new_dn_mark) |
3c5119c0 EP |
379 | destroy = 1; |
380 | goto out; | |
381 | } | |
1da177e4 | 382 | |
3c5119c0 EP |
383 | error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); |
384 | if (error) { | |
385 | /* if we added, we must shoot */ | |
ef5e2b78 | 386 | if (dn_mark == new_dn_mark) |
3c5119c0 EP |
387 | destroy = 1; |
388 | goto out; | |
1da177e4 | 389 | } |
3c5119c0 | 390 | |
ef5e2b78 EP |
391 | error = attach_dn(dn, dn_mark, id, fd, filp, mask); |
392 | /* !error means that we attached the dn to the dn_mark, so don't free it */ | |
3c5119c0 EP |
393 | if (!error) |
394 | dn = NULL; | |
395 | /* -EEXIST means that we didn't add this new dn and used an old one. | |
396 | * that isn't an error (and the unused dn should be freed) */ | |
397 | else if (error == -EEXIST) | |
398 | error = 0; | |
399 | ||
ef5e2b78 | 400 | dnotify_recalc_inode_mask(fsn_mark); |
3c5119c0 | 401 | out: |
ef5e2b78 | 402 | spin_unlock(&fsn_mark->lock); |
3c5119c0 EP |
403 | |
404 | if (destroy) | |
ef5e2b78 | 405 | fsnotify_destroy_mark(fsn_mark); |
3c5119c0 EP |
406 | |
407 | fsnotify_recalc_group_mask(dnotify_group); | |
408 | ||
409 | mutex_unlock(&dnotify_mark_mutex); | |
ef5e2b78 | 410 | fsnotify_put_mark(fsn_mark); |
3c5119c0 | 411 | out_err: |
ef5e2b78 EP |
412 | if (new_fsn_mark) |
413 | fsnotify_put_mark(new_fsn_mark); | |
3c5119c0 EP |
414 | if (dn) |
415 | kmem_cache_free(dnotify_struct_cache, dn); | |
416 | return error; | |
1da177e4 | 417 | } |
1da177e4 LT |
418 | |
419 | static int __init dnotify_init(void) | |
420 | { | |
3c5119c0 | 421 | dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC); |
ef5e2b78 | 422 | dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC); |
3c5119c0 | 423 | |
0d2e2a1d | 424 | dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); |
3c5119c0 EP |
425 | if (IS_ERR(dnotify_group)) |
426 | panic("unable to allocate fsnotify group for dnotify\n"); | |
1da177e4 LT |
427 | return 0; |
428 | } | |
429 | ||
430 | module_init(dnotify_init) |